1. Fundamentals - Aimanizales/Javascript_learning GitHub Wiki

• Globally scoped or function scoped.
• Can be re-declared.
• Hoisted¹ to the top of their scope and initialized = undefined.

• Block-scoped² (only available for use within that block. eg: if/else, function, object...)
• Can be updated but no re-declared (unless it's declared inside a block).
• Hoisted to the top but not initialized like var.

• Block-scoped like let.
• Cannot be updated nor re-declared.
• Must be initialized at the time of declaration.
• Objects initialized with const cannot be updated...
• ...but its properties can be updated.
• Hoisted to the top without value (like let).

https://www.freecodecamp.org/news/var-let-and-const-whats-the-difference/

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The current context of execution.

• The context where values and expressions are "visible" or can be referenced.

• Can be layered in a hierarchy (child scopes have access to parent scopes, but not vice versa).

• There are two types: global and local.

  • Global: variables declared outside of a block (function that serves as a closure).
  • Local: variables declared inside of a block.

https://developer.mozilla.org/en-US/docs/Glossary/Scope

https://www.digitalocean.com/community/tutorials/understanding-variables-scope-hoisting-in-javascript

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It's a JavaScript mechanism where variables and function declarations are moved to the top of their scope before code execution.

How it works?

1. Execute a JS code.
2. The JavaScript engine creates a Global Execution Context (GEC) in two phases:

• Phase 1 (creation):
  • JS engine moves variable and function declarations to the top of your code (hoisting).
  • JS engine places the function(s) declaration(s) in the heap memory.
• Phase 2: The code is executed.

Function hoisting JavaScript engine also hoists the function declarations.

https://developer.mozilla.org/en-US/docs/Glossary/Hoisting https://www.javascripttutorial.net/javascript-hoisting/

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(1) Block: a chunk of code bounded by {}