original file name: Codeium Chat - dB51IVSgh92srPpdlNtebbCFL14ggBZR.md summary: The chat conversation primarily focused on troubleshooting performance issues in a React application causing browser hangs. The user shared code snippets related to event listeners, component structure, and lifecycle methods, seeking advice to optimize the code.

The assistant provided recommendations on addressing memory leaks, inefficient rendering, state updates, large component trees, and complex computations. It suggested reviewing code for code smells, updating event listener handling, and converting class components to functional components with hooks for better performance.

Note: This is purely the output of the chat conversation and does not contain any raw data, codebase snippets, etc. used to generate the output.

User at 7:58 pm, Jun 4, 2024

My app is functioning but it causes the browser to hang and I have to keep restarting the browser.

I am monitoring memory and performance metrics in the browser but I would like to review the code involved to look for code smells or React anti-patterns or known problems.

Codeium at 7:58 pm, Jun 4, 2024

Given the complexity of browser hangs, it's necessary to look for common issues that could cause such behavior. Here are several areas and potential code smells or anti-patterns to review in a React application:

1. Memory Leaks:

   • Ensure that any listeners or subscriptions are properly cleaned up in the componentWillUnmount lifecycle method or the cleanup function of the useEffect hook. For example, make sure that event listeners added to the window or document are removed when the component unmounts.

2. Inefficient Rendering:

   • Verify that components do not re-render unnecessarily. This can be caused by passing new objects or functions as props on every render.
   • Use React.memo for functional components and shouldComponentUpdate for class components to prevent unnecessary renders.
   • Check for deep object comparisons in shouldComponentUpdate or inside useEffect dependencies array, which can be costly.

3. State Updates in Loops:

   • Look for any state updates that might be happening inside loops or intervals, which could lead to excessive re-rendering.

4. Large Component Trees:

   • A very large component tree can cause performance issues. Consider splitting components into smaller, reusable ones.

5. Complex Computations in Render:

   • Avoid doing complex computations or data transformations directly in the render method. Use memoization techniques or move them to useMemo hooks.

6. Uncontrolled Component State:

   • Ensure that you're not mixing controlled and uncontrolled components, as this can lead to unexpected behavior.

For your specific case, you might want to review the following based on your provided code:

• Look into requestAnimationFrame calls in {BaseCharacter.tsx:updatePositionAndAnimate}. Make sure to cancel these in the cleanup phase to prevent memory leaks.
• Review {HandexTerm.tsx:parseCommand} to ensure commands are processed efficiently without causing any blocking operations.
• Check for any state updates that might be triggered in rapid succession, as seen in {HandexTerm.tsx:parseCommand}.
• Confirm that {TerminalGame.tsx} and {BaseCharacter.tsx} methods that update positions and animations are optimized and not causing excessive re-renders or layout recalculations.
• Ensure that {XtermAdapter.tsx} and the fitAddon are not causing layout thrashing by triggering multiple reflows or repaints.

To further investigate, provide more information or specific code snippets that you suspect could be causing issues.

User at 9:30 pm, Jun 4, 2024

How do I do I make sure of this?

"make sure that event listeners added to the window or document are removed when the component unmounts."

Codeium at 9:30 pm, Jun 4, 2024

To ensure that event listeners added to the window or document are removed when a React component unmounts, you will need to implement cleanup logic. This is done differently depending on whether you're using class components or functional components with hooks.

In a class component, you add event listeners in the componentDidMount lifecycle method and remove them in the componentWillUnmount lifecycle method. Here's an example:

class MyComponent extends React.Component {
  handleResize = () => {
    // Handle the resize event
  };

  componentDidMount() {
    window.addEventListener('resize', this.handleResize);
  }

  componentWillUnmount() {
    window.removeEventListener('resize', this.handleResize);
  }

  render() {
    return <div>My Component</div>;
  }
}

In a functional component, you use the useEffect hook to add event listeners and return a cleanup function that removes them. Here's an example:

import React, { useEffect } from 'react';

const MyComponent = () => {
  const handleResize = () => {
    // Handle the resize event
  };

  useEffect(() => {
    // Add the event listener
    window.addEventListener('resize', handleResize);

    // Return a cleanup function
    return () => {
      // Remove the event listener
      window.removeEventListener('resize', handleResize);
    };
  }, []); // Empty dependency array ensures this effect runs once on mount and cleanup on unmount

  return <div>My Component</div>;
};

In the context of your code, you should ensure that {HandexTerm.tsx:addTouchListeners} adds listeners correctly, and you should implement a corresponding cleanup logic in {HandexTerm.tsx:removeTouchListeners} to be called when the component unmounts. If HandexTerm is a class component, place the call to removeTouchListeners inside componentWillUnmount. If it's a functional component, return removeTouchListeners from a useEffect cleanup function.

User at 9:04 am, Jun 5, 2024

I think my only addEventListener is in HandexTerm because I think that is not how React typically expects to handle event listeners, and I have been trying to follow the most advanced React best practices. I'm sure I have fallen short because I am a React newb, so I need your help addressing the code debt I have accumulated in the interest of just getting this working.

I think this handles all the addEventListener issues, but I would like to loop back to each of your other recommendations that might apply.

 addTouchListeners() {
  // Assuming 'terminalElementRef' points to the div you want to attach the event
  const div = this.terminalElementRef.current;
  if (div) {
   div.addEventListener('touchmove', this.handleTouchMove, { passive: false });
  }
  const output = window.document.getElementById(TerminalCssClasses.Output);
  if (output) {
   output.addEventListener('touchmove', this.handleTouchMove, { passive: false });
  }
  const terminal = document.getElementById(TerminalCssClasses.Terminal);
  if (terminal) {
   terminal.addEventListener('touchmove', this.handleTouchMove, { passive: false });
  }
 }

 removeTouchListeners() {
  const div = this.terminalElementRef.current;
  if (div) {
   div.removeEventListener('touchmove', this.handleTouchMove);
  }
  const output = window.document.getElementById(TerminalCssClasses.Output);
  if (output) {
   output.removeEventListener('touchmove', this.handleTouchMove);
  }
  const terminal = document.getElementById(TerminalCssClasses.Terminal);
  if (terminal) {
   terminal.removeEventListener('touchmove', this.handleTouchMove);
  }
 }

I also want to address anything that might cause unnecessary overhead. For instance, I don't understand how these Ref items work, or why we ended up with multiple. 

<XtermAdapter
  ref={this.adapterRef}
  terminalElement={this.terminalElementRef.current}
  terminalElementRef={this.terminalElementRef}
  terminalFontSize={this.currentFontSize}
  onAddCharacter={this.handleCharacter.bind(this)}
  onTouchStart={this.handleTouchStart}
  onTouchEnd={this.handleTouchEnd}
/>

You mentioned in a previous conversation that functional components don't require onComponentDidMount because the code doesn't run until everything is mounted, I think. Would you recommend that I convert HandexTerm to a functional component, or would that simplify, optimize, or improve anything?

Also, are there other libraries, such as Preact Signals or React Query, which I should be using for a more expert, optimal React implementation?

Codeium at 9:05 am, Jun 5, 2024

The addTouchListeners and removeTouchListeners methods you've provided look like they handle the addition and removal of event listeners correctly. Just make sure that removeTouchListeners is called in the cleanup phase of your component's lifecycle.

Regarding the multiple ref items and the <XtermAdapter /> component:

1. Multiple Refs: It's unusual to pass both a ref and the current value of that ref as props. Generally, you should pass just the ref itself. The child component can access the current value by using the ref directly.

2. onAddCharacter Binding: In the onAddCharacter prop, you're using .bind(this), which creates a new function on each render. Instead, bind it in the constructor or use an arrow function to ensure the same function reference is used across renders.

3. Functional Components: Converting HandexTerm to a functional component could be beneficial in terms of readability and maintainability. Functional components with hooks are the modern standard in React, and they can lead to cleaner code with less boilerplate. Additionally, hooks provide a more declarative way to handle side effects, state, and refs.

   Here's a simple example of how you could convert to using hooks for event listeners:

   const HandexTerm = () => {
     const terminalElementRef = useRef(null);
   
     useEffect(() => {
       // Add event listeners
       const div = terminalElementRef.current;
       if (div) {
         div.addEventListener('touchmove', handleTouchMove, { passive: false });
       }
   
       // Cleanup function
       return () => {
         // Remove event listeners
         if (div) {
           div.removeEventListener('touchmove', handleTouchMove);
         }
       };
     }, []); // Empty dependency array means this effect runs once on mount and unmount
   
     // ... rest of your component
   }

4. Libraries:

   • Preact Signals: Preact Signals is more commonly used with Preact, a lightweight alternative to React. If you're using React, you may not need this.
   • React Query: React Query is excellent for managing server state, caching, and synchronizing data. If your application involves complex data fetching, updates, or caching, React Query could be beneficial.

Finally, you should evaluate the usage of these libraries based on the specific needs of your project. If HandexTerm is primarily dealing with terminal emulation and local component state, and not much server state, you might not need React Query. However, if you do have complex server state logic, React Query might be a good addition.

In summary, consider the following steps:

• Refactor HandexTerm to a functional component and use hooks for better lifecycle management.
• Optimize event listener logic to avoid unnecessary re-renders and memory leaks.
• Assess the need for additional libraries like React Query based on your app's requirements.

User at 9:55 am, Jun 5, 2024

Could you explain how to do this:

"onAddCharacter Binding: In the onAddCharacter prop, you're using .bind(this), which creates a new function on each render. Instead, bind it in the constructor or use an arrow function to ensure the same function reference is used across renders."

Codeium at 9:55 am, Jun 5, 2024

Certainly! When you use .bind(this) in the render method or within a JSX prop, a new function is created every time the component re-renders, which can lead to performance issues, especially if the component re-renders often.

Here's how you can address this issue:

class HandexTerm extends React.Component {
  constructor(props) {
    super(props);
    this.handleCharacter = this.handleCharacter.bind(this);
  }

  handleCharacter(character) {
    // Your handleCharacter logic
  }

  render() {
    return (
      <XtermAdapter
        ref={this.adapterRef}
        terminalElement={this.terminalElementRef.current}
        terminalElementRef={this.terminalElementRef}
        terminalFontSize={this.currentFontSize}
        onAddCharacter={this.handleCharacter} // No need to bind here
        // ... other props
      />
    );
  }
}

By binding handleCharacter in the constructor, you ensure that the same function reference is used across all renders.

You can also define handleCharacter as an arrow function, which automatically binds the function to the instance of the class.

class HandexTerm extends React.Component {
  handleCharacter = (character) => {
    // Your handleCharacter logic
  };

  render() {
    // ...
  }
}

When you define a method as an arrow function in a class property, it's bound to the class instance, and you won't need to bind it in the constructor or in the render method.

If you decide to convert HandexTerm to a functional component, you can define handleCharacter directly as an arrow function within the functional component body.

const HandexTerm = () => {
  const handleCharacter = (character) => {
    // Your handleCharacter logic
  };

  return (
    <XtermAdapter
      // ...
      onAddCharacter={handleCharacter} // Automatically bound
      // ... other props
    />
  );
};

In functional components, arrow functions capture the this context of the surrounding scope, which in the case of functional components means they don't need to be bound.

Whichever method you choose, the goal is to avoid creating new function instances on every render, which can lead to unnecessary re-renders and performance degradation, especially for child components that rely on prop equality to prevent unnecessary updates (like those wrapped in React.memo).

User at 10:26 am, Jun 5, 2024

It seems like on the path to converting to functional components, it would be good to convert class methods to arrow functions, like this:

 componentWillUnmount = () => {
  if (this.heroRunTimeoutId) {
   clearTimeout(this.heroRunTimeoutId);
  }
  this.removeTouchListeners();
 }

Codeium at 10:26 am, Jun 5, 2024

Yes, converting class methods to arrow functions can be a step towards a more functional style within class components. Arrow functions capture the this context of the class instance, so they can be particularly useful for event handlers and callbacks that you pass to other components or APIs.

However, it's important to note that lifecycle methods in class components, like componentWillUnmount, should be defined using the standard method syntax, not as arrow functions. This is because React assigns special meaning to these methods, and defining them as arrow functions could potentially cause unexpected behavior or break conventions that could confuse other developers.

Here's the correct way to define componentWillUnmount:

class MyComponent extends React.Component {
  // Other class methods...

  componentWillUnmount() {
    // Your cleanup logic
  }
}

If you're looking to convert to functional components, you wouldn't use lifecycle methods at all. Instead, you'd use the useEffect hook, which can handle side effects and includes a cleanup phase that replaces componentWillUnmount. Here's an example:

import React, { useEffect } from 'react';

const MyComponent = () => {
  useEffect(() => {
    // ComponentDidMount logic goes here

    return () => {
      // componentWillUnmount logic goes here
    };
  }, []); // Empty dependency array ensures this runs once on mount and once on unmount

  return <div>My Component</div>;
};

In the cleanup function returned by useEffect, you would include any logic that needs to run when the component unmounts, such as removing event listeners or clearing timeouts.

User at 10:29 am, Jun 5, 2024

Ok, but please explain more about why traditional lifecycle methods should be defined using the standard method syntax. What problem might arrow functions create for those methods?

Codeium at 10:29 am, Jun 5, 2024

React's class components have specific lifecycle methods, such as componentDidMount, componentDidUpdate, componentWillUnmount, etc. These methods are part of React's component API, and React expects them to be defined in a specific way to call them at the appropriate times in the lifecycle of a component.

Here's why you should use the standard method syntax for lifecycle methods instead of arrow functions:

1. Convention and Clarity: Lifecycle methods are part of the React class component API, and using the standard method definition is a convention that is expected and understood by React developers. It clearly indicates that the method is a lifecycle method with special behavior.

2. React Internals: React internally uses the prototype of the component class to recognize lifecycle methods. When you define a method using an arrow function as a class field, it becomes an instance property and not part of the prototype. React might not recognize instance properties as lifecycle methods and, therefore, will not call them at the intended points in the lifecycle.

3. Performance: Arrow functions as class fields can also lead to performance implications. Since they're instance properties, a new function is created for each instance of the class, which could lead to increased memory usage, especially if many instances of the component are created.

4. Inheritance: Defining lifecycle methods using standard method syntax allows subclasses to call super.methodName() if they need to extend the behavior of the lifecycle methods. This is not possible with arrow functions as they are not part of the class's prototype.

5. Tooling and Future Changes: Tools and future updates to React may rely on lifecycle methods being defined in the standard way. Deviating from this could lead to issues with tooling, such as linters and codemod tools, and could make future migrations more difficult.

In summary, while arrow functions are useful for handling the correct this binding for callbacks and event handlers, lifecycle methods in class components should always be defined using standard method syntax to ensure they are recognized and called by React. If you're transitioning to functional components, you'll use the useEffect hook to handle lifecycle events, and the concerns about method syntax no longer apply.

User at 11:12 am, Jun 5, 2024

I am using Performance Monitor to monitor when the application hangs and it just happened.

The CPU usage has risen to 100% JS heap size: 16 mb DOM Nodes: 1366 JS event listeners: 253 Documents: 6 Document Frames: 3 Layouts/sec: 0 Style recalcs/sec: 0

If I stop and restart I have:

CPU usage: 20% JS heap size: 8.1 mb DOM Nodes: 421 JS Event Listeners 224 Documents: 1 etc

Does this indicate any code anit-patterns I should look for?

Codeium at 11:13 am, Jun 5, 2024

The monitoring data you've provided indicates several potential issues that can be common in web applications causing high CPU usage and browser hangs:

1. JS Heap Size Increase: A doubling of the heap size could indicate a memory leak. Memory leaks occur when memory that is no longer needed is not released. Look for:

   • Variables or data structures that grow unbounded over time.
   • Closures that retain large amounts of data or DOM elements unnecessarily.
   • Components that are not unmounted properly.

2. High Number of DOM Nodes: A large number of DOM nodes can slow down the application, especially if there are complex CSS selectors or frequent DOM manipulations. Check for:

   • Unnecessary rendering of components or elements.
   • Components that add DOM nodes but don't properly remove them when they're unmounted.

3. JS Event Listeners: A high number of JS event listeners can be a sign of event listeners not being cleaned up. This is often related to memory leaks. Ensure that:

   • All event listeners are removed when they're no longer needed, such as when a component unmounts.
   • Event listeners are not added repeatedly, such as in a componentDidUpdate or useEffect without proper cleanup.

4. Multiple Documents: Having more documents than expected might indicate iframes or popups that are not being managed correctly. Check for:

   • Iframes or windows created programmatically that aren't being removed properly.
   • Unnecessary usage of iframes or external documents.

The increase in CPU usage and JS heap size when the application hangs, followed by a decrease after a restart, suggests a possible memory leak or inefficient resource management.

Here are steps you can take to diagnose and address these issues:

• Profile the Application: Use the Performance and Memory tabs in the browser's developer tools to record sessions and take heap snapshots. Analyze the recordings and snapshots to identify functions that take a long time or grow in memory usage over time.
• Audit Event Listeners: Check your components that add event listeners to ensure they have corresponding logic to remove those listeners.
• Review Component Mounting: Ensure that components are unmounted correctly, and their effects are cleaned up to avoid memory leaks.
• Optimize Rendering: Limit re-renders by using React.memo for functional components, shouldComponentUpdate for class components, and by optimizing the use of React hooks like useMemo and useCallback.
• Check for Infinite Loops: Look for any setInterval, recursive setTimeout, or requestAnimationFrame callbacks that might be running indefinitely and ensure they are cleared properly.

By methodically checking each of these areas and applying best practices for cleanup and optimization, you should be able to identify and resolve the causes of the high CPU usage and application hangs.

User at 11:47 am, Jun 5, 2024

I am definitely createing too many DOM Nodes and not destroying them.

It's probably mostly in NextCharsDisplay when I use my custom CreateElement like this:

  constructor(props: NextCharsDisplayProps) {
    super(props);
    this._errorDisplayRef = createRef();
    this.voiceSynth = window.speechSynthesis as SpeechSynthesis;
    this._nextChars = document.getElementById(TerminalCssClasses.NextChars) as HTMLElement;
    this._nextCharsRate = document.getElementById(TerminalCssClasses.NextCharsRate) as HTMLDivElement;
    this._wpm = createElement('div', TerminalCssClasses.WPM) as HTMLSpanElement;
    this._charTimes = createElement('div', TerminalCssClasses.CharTimes);
    this._chordImageHolder = document.querySelector(`#${TerminalCssClasses.ChordImageHolder}`) as HTMLElement;
    this._svgCharacter = createElement('img', TerminalCssClasses.SvgCharacter);
    this._testArea = (document.getElementById(TerminalCssClasses.TestArea) as HTMLTextAreaElement);
    this.isTestMode = localStorage.getItem('testMode') == 'true';
    this._timerRef = createRef();
    // this._timer = new Timer();
  }

From src/utils/dom.ts

export function createElement<T extends HTMLElement>(tagName: keyof HTMLElementTagNameMap, className?: string): T {
  const element = document.createElement(tagName) as T;
  if (className) {
    element.id = className;
    element.classList.add(className);
  }
  return element;
}

export function createHTMLElementFromHTML(htmlString: string): HTMLElement {
  const parser = new DOMParser();
  const doc = parser.parseFromString(htmlString, 'text/html');
  return doc.body.firstChild as HTMLElement;
}

Maybe that would be better to implement as a functional component, or maybe I just need to figure out how to destroy every node when I am done using it.

Codeium at 11:47 am, Jun 5, 2024

Creating DOM elements directly in React components, as you're doing in your NextCharsDisplay constructor, can indeed lead to issues like uncontrolled growth of the DOM tree, which can become a source of memory leaks and performance bottlenecks. React components should manage the DOM through the virtual DOM to avoid such issues.

Here's how you can refactor your code to address this:

Converting NextCharsDisplay to a functional component and using JSX to create elements would let React handle the lifecycle of the DOM nodes, which includes their creation and destruction. Here's a conceptual example of what that might look like:

const NextCharsDisplay = (props: NextCharsDisplayProps) => {
  const errorDisplayRef = useRef(null);
  const timerRef = useRef(null);
  const isTestMode = localStorage.getItem('testMode') === 'true';

  // Use state hooks for dynamic values
  const [nextChars, setNextChars] = useState<string>('');

  // You can use useEffect for any setup that needs to run on component mount
  useEffect(() => {
    // Perform any setup here

    return () => {
      // Cleanup code here
    };
  }, []); // Empty dependency array ensures this runs once on mount and once on unmount

  return (
    <div>
      {/* Replace createElement calls with JSX */}
      <div id={TerminalCssClasses.WPM} className={TerminalCssClasses.WPM}></div>
      <div id={TerminalCssClasses.CharTimes} className={TerminalCssClasses.CharTimes}></div>
      {/* ... rest of your component ... */}
    </div>
  );
};

Using JSX allows React to create and manage the elements efficiently. When the component unmounts, React will automatically clean up the DOM nodes it created.

If you need to create and remove elements imperatively for some reason, you should handle the destruction of those nodes in the cleanup function of a useEffect hook. You should also ensure that any global side effects (like adding event listeners to window or document) are cleaned up in this function.

Here's an example:

useEffect(() => {
  // Imperative DOM node creation (if absolutely necessary)
  const myElement = document.createElement('div');
  document.body.appendChild(myElement);

  return () => {
    // Remove the element when the component unmounts
    document.body.removeChild(myElement);
  };
}, []); // Empty dependency array for component mount/unmount

Using React's declarative approach with JSX is the preferred way to manage DOM elements, as it allows React to optimize rendering and cleanup. If you must create elements outside of React's control, make sure to pair each creation with a destruction in the cleanup phase to prevent memory leaks.

Refactoring NextCharsDisplay to a functional component and using JSX for rendering will likely resolve the issues you're experiencing with DOM node management. If you have imperative code that needs to directly interact with the DOM, always ensure you have corresponding cleanup logic.

User at 11:56 am, Jun 5, 2024

If I convert my NextCharsDisplay to a functional component as you've suggested, how do I call it from HandTerm?

Codeium at 11:57 am, Jun 5, 2024

Once you've converted NextCharsDisplay to a functional component, you can call it from HandTerm just as you would with any other React component, by including it in the JSX of HandTerm's render method or function body.

Here's a conceptual example of how you might do this:

import NextCharsDisplay from './NextCharsDisplay';

const HandTerm = () => {
  // State and logic for HandTerm...

  return (
    <div>
      {/* Other components and JSX */}
      <NextCharsDisplay
        commandLine={/* state or props value */}
        onTimerStatusChange={/* callback function */}
        isInPhraseMode={/* state or props boolean */}
        onNewPhrase={/* callback function */}
        onPhraseSuccess={/* callback function */}
      />
      {/* More components and JSX */}
    </div>
  );
};

export default HandTerm;

In the JSX above, <NextCharsDisplay /> is included just like any other component. You pass props to it as needed, based on the state, props, and callbacks of HandTerm.

If HandTerm is a class component, the usage is similar; you would include <NextCharsDisplay /> in the render method of the class:

import React from 'react';
import NextCharsDisplay from './NextCharsDisplay';

class HandTerm extends React.Component {
  // Class methods and state...

  render() {
    return (
      <div>
        {/* Other components and JSX */}
        <NextChars/Display
          commandLine={/* state or props value */}
          onTimerStatusChange={/* callback function */}
          isInPhraseMode={/* state or props boolean */}
          onNewPhrase={/* callback function */}
          onPhraseSuccess={/* callback function */}
        />
        {/* More components and JSX */}
      </div>
    );
  }
}

export default HandTerm;

Remember to replace the placeholders (e.g., /* state or props value */) with actual state variables, props, or methods from HandTerm. The props you pass to NextCharsDisplay should correspond to the expected prop types defined in NextCharsDisplayProps.

User at 12:02 pm, Jun 5, 2024

If I eliminate CreateElement but creating components with JSX as you recommended, how do I refer to the created items?

return (
    <div>
      {/* Replace createElement calls with JSX */}
      <div id={TerminalCssClasses.WPM} className={TerminalCssClasses.WPM}></div>
      <div id={TerminalCssClasses.CharTimes} className={TerminalCssClasses.CharTimes}></div>
      {/* ... rest of your component ... */}
    </div>
  );

Codeium at 12:02 pm, Jun 5, 2024

In React, when you want to reference a DOM element created with JSX, you use refs. The useRef hook is the way to create refs in functional components. Here's how you can update your component to use refs:

import React, { useRef } from 'react';

const NextCharsDisplay = (props) => {
  // Create refs for the elements you want to reference
  const wpmRef = useRef(null);
  const charTimesRef = useRef(null);

  // Rest of your component logic...

  return (
    <div>
      {/* Attach the refs to the elements */}
      <div id={TerminalCssClasses.WPM} className={TerminalCssClasses.WPM} ref={wpmRef}></div>
      <div id={TerminalCssClasses.CharTimes} className={TerminalCssClasses.CharTimes} ref={charTimesRef}></div>
      {/* ... rest of your component ... */}
    </div>
  );
};

export default NextCharsDisplay;

With these refs, you can access the underlying DOM elements directly if necessary. For example:

// Inside a useEffect or a function
if (wpmRef.current) {
  console.log(wpmRef.current); // This is the actual DOM node
  // You can directly manipulate the DOM element if needed
  wpmRef.current.textContent = 'New content';
}

Remember that direct manipulation of the DOM should be avoided in React unless it's absolutely necessary, as it can lead to inconsistencies between the actual DOM and React's virtual DOM. Instead, it's best to use React's state and props to control your component's output and behavior.

User at 12:49 pm, Jun 5, 2024

Ok, so I am looking at converting NextCharsDisplay to a functional component.

One thing I am noticing is that it has getters and setters for properties, some of which might be read only.

How would I handle that with a functional component?

Codeium at 12:50 pm, Jun 5, 2024

In functional components, getters and setters from class components are typically replaced by React's state and effect hooks. Here's how you can approach different scenarios:

If you have read-only properties, these can often be derived from props or state within the component. You would use the state directly or compute the values on-the-fly within the component's body or a useEffect hook.

For properties that hold state and need getters and setters, you would use the useState hook. Here's an example:

const [myProperty, setMyProperty] = useState(initialValue);

To read the value, you simply use myProperty. To update it, you call setMyProperty(newValue).

If you have a complex getter that computes a value based on the state, you can use the useMemo hook:

const myComplexProperty = useMemo(() => {
  // Compute the value based on props or state
  return computeSomeValue(props.someValue);
}, [props.someValue]); // Dependencies for when to recompute

If you need to perform side effects when a property changes, similar to how you might have used setters in a class component, you would use the useEffect hook:

useEffect(() => {
  // Perform side effects here using myProperty
}, [myProperty]); // Dependencies array tells React to run this effect when myYroperty changes

If you need to expose functions (similar to public methods in a class) to parent components, you can use the useImperativeHandle hook in combination with forwardRef:

const NextCharsDisplay = forwardRef((props, ref) => {
  useImperativeHandle(ref, () => ({
    myPublicFunction: () => {
      // This function can be called by the parent component
    }
  }));

  // Component logic...
});

The parent component can then call myPublicFunction on the ref provided to NextCharsDisplay.

By using these hooks, you can replicate the behavior of getters, setters, and instance methods from class components within functional components. Remember to follow React's declarative patterns as closely as possible and only use imperative code when it's the only solution.

User at 12:54 pm, Jun 5, 2024

That is very helpful information. I am going to be doing some of that.

At the moment, that seems like a lot of work that might leave my code in a non-functioning state until I can complete the edit.

Before doing that, is there a way to just use the JSX render of the DOM elements one-by-one, so that I can edit and watch the result?

Let's start with this one:

    this._nextChars = document.getElementById(TerminalCssClasses.NextChars) as HTMLElement;

Codeium at 12:54 pm, Jun 5, 2024

Certainly! You can incrementally replace direct DOM manipulations with JSX in your class component's render method. This allows you to see the results of each change without having to refactor the entire component at once.

Here's how you can start by replacing the line where you get the _nextChars element by ID with JSX:

1. Remove the line from the constructor that assigns _nextChars to a DOM element.
2. Add a ref to your class to keep a reference to the _nextChars element.
3. Use the ref in the render method to reference the element in JSX.

Here's what the changes might look like:

class NextCharsDisplay extends React.Component {
  _nextCharsRef = React.createRef(); // Step 2: Create a ref

  // ... other component logic ...

  render() {
    return (
      <div>
        {/* ... other JSX ... */}

        {/* Step 3: Use the ref in JSX */}
        <div id={TerminalCssClasses.NextChars} ref={this._nextCharsRef}></div>

        {/* ... more JSX ... */}
      </div>
    );
  }
}

Now, wherever you were using this._nextChars to directly manipulate the DOM, you would instead use this._nextCharsRef.current. For example:

componentDidMount() {
  if (this._nextCharsRef.current) {
    this._nextCharsRef.current.textContent = 'Some content';
  }
}

Remember that direct DOM manipulation in React should generally be avoided. You should use React's state system to handle changes to the DOM wherever possible. This example is simply a stepping stone to help you transition away from direct DOM manipulation towards a more React-centric approach.

Once you've replaced all direct DOM manipulations with JSX and refs, you can then proceed to convert the entire component to a functional component using hooks, as discussed earlier.

User at 1:10 pm, Jun 5, 2024

That means I have to declare _nextCharsRef as a React.refObj<any>.

That causes subsequent errors everywhere I want to use it:

  cancelTimer = () => {
    if (this._timerRef.current) {
      this._timerRef.current.reset();
    }
    if (this._nextCharsRef) this._nextCharsRef.innerText = this.state.phrase.value;
    if (this._testArea) {
      this._testArea.style.border = "2px solid lightgray";
      this._testArea.disabled = false;
      this._testArea.value = '';
      this._testArea.focus();
    }
  }

  reset(): void {
    this.state.phrase = new Phrase('');
    this.setNext('');
    this._nextCharsRef.hidden = true;
  }

  public get nextChars(): HTMLElement {
    return this._nextCharsRef;
  }

How should I handle that?

Will that issue be reduced when I convert NextCharsDisplay to a React functional component?

Codeium at 1:10 pm, Jun 5, 2024

When you're using refs in React, the correct way to access the referenced DOM element is through the current property of the ref object. So instead of this._nextCharsRef.innerText or this._nextCharsRef.hidden, you should use this._nextCharsRef.current.innerText and this._nextCharsRef.current.hidden.

Here's how you can update the cancelTimer and reset methods:

cancelTimer = () => {
  if (this._timerRef.current) {
    this._timerRef.current.reset();
  }
  if (this._nextCharsRef.current) {
    this._nextCharsRef.current.innerText = this.state.phrase.value;
  }
  // ... rest of your logic ...
}

reset = () => {
  // ... rest of your logic ...
  if (this._nextCharsRef.current) {
    this._nextCharsRef.current.hidden = true;
  }
}

And for the getter nextChars, you should return this._nextCharsRef.current:

public get nextChars(): HTMLElement | null {
  return this._nextCharsRef.current;
}

Make sure to check if this._nextCharsRef.current is not null before accessing it, as it will be null until the component has been mounted and the ref has been attached to a DOM element.

Yes, when you convert NextCharsDisplay to a functional component and use hooks, the way you handle refs will be different and often simpler. You would use the useRef hook to create refs, and because hooks are used within the body of the component function, you don't need this.

Here's a conceptual example of how your functional component might manage a ref:

const NextCharsDisplay = () => {
  const nextCharsRef = useRef<HTMLElement>(null);
  const [phrase, setPhrase] = useState(new Phrase(''));

  // Example of a function using the ref
  const reset = () => {
    setPhrase(new Phrase(''));
    if (nextCharsRef.current) {
      nextCharsRef.current.hidden = true;
    }
  };

  // ... rest of your component ...

  return (
    <div>
      <div ref={nextCharsRef} />
      {/* ... rest of your JSX ... */}
    </div>
  );
};

In a functional component, you can access the ref directly with nextCharsRef.current without worrying about the this binding. Remember that refs in functional components will persist for the full lifetime of the component, just like in class components.

User at 2:42 pm, Jun 5, 2024

As I reassign some of these document.createElement items to JSX <span> for instance, I get the message "Type 'HTMLSpanElement' is not assignable to type 'LegacyRef | undefined'.ts(2322)"

The React.objRef<any> is legacy?

When will I be upgrading to the newer version?

Codeium at 2:43 pm, Jun 5, 2024

The message you're encountering seems to be a TypeScript type error related to the assignment of refs. Let's clarify a few things to address this error:

1. Ref Creation: When creating a ref in TypeScript with React, use React.createRef for class components or useRef for functional components. Here is how you declare those refs:

   • Class component:

     class MyComponent extends React.Component {
       private myRef = React.createRef<HTMLSpanElement>();
       // ...
     }

   • Functional component:

     const MyComponent = () => {
       const myRef = useRef<HTMLSpanElement>(null);
       // ...
     }

2. Ref Assignment: When you use a ref in JSX, you assign it to the ref attribute of a JSX element:

   <span ref={this.myRef}>...</span>

   or for functional components:

   <span ref={myRef}>...</span>

3. Type 'HTMLSpanElement' is not assignable: This error typically means that you are trying to assign a DOM element directly to a ref object, which is incorrect. You should only assign the ref object to the ref attribute in JSX. React will take care of attaching the DOM element to the current property of the ref.

4. Legacy Refs: The term LegacyRef refers to the older callback ref style, which is not the issue here. However, it is recommended to use the createRef and useRef hooks as shown above, which are the current standard in React for creating refs.

5. Upgrading to a Newer Version: If you're using a modern version of React (16.3+), you're already using the recommended approach for refs with createRef and useRef. If you see a message about legacy refs, it is likely referring to the older callback ref pattern, which looks like this:

   <span ref={(element) => { this.myRef = element; }}>...</span>

   This older pattern is not recommended for new code and should be replaced with createRef or useRef.

To resolve your TypeScript error, ensure that you're using createRef or useRef correctly and assigning the ref object to the ref attribute in JSX. If you're still encountering issues, please provide more context or a code snippet where the error occurs, and I can give you more targeted advice.

User at 3:26 pm, Jun 5, 2024

I think I may have misunderstood something.

Ealier, you said I could create a DOM element more appropriately than what I had been doing by putting this in my render()

        <div id={TerminalCssClasses.NextChars} ref={this._nextCharsRef}></div>

And putting this in my constructor()

    this._nextCharsRef = React.createRef();

But that necessitated putting this in my variable declarations:

  private _nextCharsRef: React.RefObject<any>;

Is that non-optimal?

Codeium at 3:27 pm, Jun 5, 2024

The way you've declared your ref is almost correct, but it's better to avoid using the any type when you know the type of element the ref will point to. Instead, you should specify the type of the DOM element that the ref will be attached to for better type safety.

If _nextCharsRef is a reference to a div element, you should declare it as a RefObject pointing to an HTMLDivElement. Here's how you can declare and initialize the ref in your class component:

class MyComponent extends React.Component {
  private _nextCharsRef: React.RefObject<HTMLDivElement>;

  constructor(props) {
    super(props);
    this._nextCharsRef = React.createRef<HTMLDivElement>(); // Specify the element type
  }

  render() {
    return (
      <div id={TerminalCssClasses.NextChars} ref={this._nextCharsRef}></div>
    );
  }

  // ... rest of your class ...
}

By specifying HTMLDivElement as the generic type for React.createRef, TypeScript will know that _nextCharsRef.current will be an HTMLDivElement (or null if the ref has not been attached to any element yet). This provides better type checking and autocompletion when you access the ref later in your code.

The use of React.createRef and RefObject is optimal for class components in modern React. For functional components, you would use the useRef hook instead, which has a similar type parameter for specifying the type of the referenced element.

User at 4:34 pm, Jun 5, 2024

I am rendering <Timer> like this:

        <Timer
          ref={this._timerRef}
        />

and I'm getting this error:

Type '{ ref: RefObject<any>; }' is not assignable to type 'IntrinsicAttributes'.
  Property 'ref' does not exist on type 'IntrinsicAttributes'.ts(2322)
⚠ Error (TS2322)  | 
Type  { ref: RefObject<any> } 
 is not assignable to type  IntrinsicAttributes 

I'm declaring the Timer like this:

xport const Timer: React.FC = forwardRef((_props: any, ref: any) => {

Codeium at 4:34 pm, Jun 5, 2024

The error you're seeing suggests that TypeScript isn't recognizing that <Timer> can accept a ref prop. This is likely because the Timer component is not declaring the types for its props and ref correctly.

When using forwardRef in TypeScript, you should specify the type of the ref that your component will accept. Additionally, if your component accepts no props, it's better to specify an empty object {} instead of any to indicate this clearly. Here's how you should declare Timer:

import React, { forwardRef } from 'react';

export const Timer: React.ForwardRefExoticComponent<React.RefAttributes<YourRefType>> = forwardRef(
  (_props, ref) => {
    // Your Timer component implementation
  }
);

Replace YourRefType with the type of the ref you are expecting (e.g., HTMLDivElement if it's a div). If you're not sure about the type or if it's a custom component, you can use HTMLElement as a generic type or the specific type that matches your usage.

Now, when rendering the Timer component and passing a ref, TypeScript should not complain:

<Timer ref={this._timerRef} />

Make sure that _timerRef is declared with the correct type in the component that's rendering <Timer>. For example:

class MyComponent extends React.Component {
  private _timerRef: React.RefObject<HTMLDivElement>; // Assuming Timer uses a div element

  constructor(props) {
    super(props);
    this._timerRef = React.createRef<HTMLDivElement>();
  }

  render() {
    return <Timer ref={this._timerRef} />;
  }
}

If Timer is a custom component and not a standard HTML element, you should declare the ref type according to the element type that Timer uses internally or the instance type of the Timer component itself.

If you continue to have issues, you might need to verify that Timer correctly forwards the ref to the underlying DOM element or class instance, and you might need to adjust the type definitions accordingly.

User at 7:01 pm, Jun 5, 2024

How do I assign innerText to one of the HTMLElement items?

This gives me an error:

  set wpm(wpm: HTMLSpanElement) {
    if(this._wpmRef.current) this._wpmRef.current.innerText = wpm;
  }

Codeium at 7:01 pm, Jun 5, 2024

The error you're encountering is likely due to a type mismatch. The wpm setter is expecting an HTMLSpanElement as its parameter, but you're trying to assign it to innerText, which is a string property.

The innerText property of an HTMLElement should be set to a string, not to an HTMLSpanElement. Here's how you can correct the setter:

set wpm(value: string) {
  if (this._wpmRef.current) {
    this._wpmRef.current.innerText = value;
  }
}

Make sure that wherever you're calling the wpm setter, you're passing a string as the argument:

this.wpm = "Your new value";

This will correctly update the innerText of the element referenced by _wpmRef.

User at 7:19 pm, Jun 5, 2024

I am getting this error:

Type 'RefObject<HTMLImageElement>' is missing the following properties from type 'HTMLImageElement': align, alt, border, complete, and 322 more.ts(2740)
ErrorDisplay.tsx(4, 3): The expected type comes from property 'svgCharacter' which is declared here on type 'IntrinsicAttributes & ErrorDisplayProps & RefAttributes<unknown>'

When I try to assign these properties.

        <ErrorDisplay
          isVisible={this.state.mismatchedIsVisible}
          ref={this._errorDisplayRef}
          svgCharacter={this._svgCharacter}
          chordImageHolder={this._chordImageHolderRef}
          mismatchedChar={this.state.mismatchedChar}
          mismatchedCharCode={this.state.mismatchedCharCode}
        />

Codeium at 7:20 pm, Jun 5, 2024

The error message is indicating that you're trying to pass a RefObject to the svgCharacter prop, but ErrorDisplay is expecting an HTMLImageElement instead. In React, refs have a current property that holds the actual DOM element reference, which is what you typically want to pass around, not the ref object itself.

Here's how you can fix the issue:

Instead of passing the ref object directly to svgCharacter, pass the current property of the ref, which should be the actual HTMLImageElement (or null if the ref hasn't been attached yet):

<ErrorDisplay
  isVisible={this.state.mismatchedIsVisible}
  ref={this._errorDisplayRef}
  svgCharacter={this._svgCharacter.current} // Pass the current DOM element
  chordImageHolder={this._chordImageHolderRef.current} // Also pass the current DOM element
  mismatchedChar={this.state.mismatchedChar}
  mismatchedCharCode={this.state.mismatchedCharCode}
/>

Make sure that the ErrorDisplay component's props are typed correctly to accept HTMLImageElement | null and HTMLDivElement | null for svgCharacter and chordImageHolder, respectively. For example, in ErrorDisplayProps interface:

interface ErrorDisplayProps {
  isVisible: boolean;
  svgCharacter: HTMLImageElement | null;
  chordImageHolder: HTMLDivElement | null;
  mismatchedChar: string;
  mismatchedCharCode: string;
}

Lastly, ensure that ErrorDisplay is using forwardRef if you intend to pass a ref to it. This allows the component to forward the ref to a child DOM element or component. Here's an example of how ErrorDisplay might be defined:

const ErrorDisplay = forwardRef<YourElementType, ErrorDisplayProps>((props, ref) => {
  // Use ref as needed within the component
  return (
    // ... JSX ...
  );
});

Replace YourElementType with the type of element or component instance that this ref will be referring to (HTMLDivElement, HTMLImageElement, etc.). If ErrorDisplay is a functional component and you don't need to use ref inside it, then you don't need to use forwardRef.