Salsa

Salsa is the code name for the effort to add JavaScript support to the TypeScript compiler and language service. The goal is to have the TypeScript language service replace the existing JavaScript language services across Visual Studio, VS Code, and other editors we support. This fork is intended to serve as centralized location for feedback, bug reporting, and general documentation.

Automatic Typing Acquisition

Overview

The new language service requires TypeScript definition (.d.ts) files to power IntelliSense when types can’t be inferred by the TypeScript compiler. For external libraries, most of these .d.ts files can be found in the GitHub repository Definitely Typed. Fetching them manually can be tedious, so we created a new feature that infers external library dependencies for your project and then automatically downloads the corresponding TypeScript definition files to enhance IntelliSense for those libraries.

For example, if you have the dependency "jquery" in your package.json, the feature will download the "jquery.d.ts" to [Your project root]\typings folder, and use it to enhance IntelliSense during your editing session. Note that the feature will also create a tsd.json file at your project root path as a registry for acquired typing files, so that next time the downloaded jquery.d.ts can be used directly without downloading.

To enable this feature: Create a tsconfig.json or jsconfig.json file in your project root. NOTE: The schema of tsconfig.json and jsconfig.json is the same, and can be found here. If a tsconfig.json file is used, make sure to set the allowJs compiler option to true, otherwise no .js files will be included in the project. The config file might look like this:

{
    "compilerOptions": {
        "allowJs": true
    },
    "exclude": [
        "typings",
        "node_modules"
    ],
    "typingOptions": {
        "enableAutoDiscovery": true
    }
}

Open a .js file in VS Code, and you will see a typings folder being created with downloaded .d.ts files in it.

Customize the typing experience

There are several typingOptions available to decide what typing files to use:

• enableAutoDiscovery: a boolean value deciding to automatically infer typing information or not. If set to true, the language service will look for typing information from the following sources:

  • dependencies property in common config files in project root level For example, package.json and bower.json
  • installed node packages in node_modules folder, if there is any
  • .d.ts files came with installed node module
  • loose JavaScript files that has the name of common libraries If the project contains a file named jquery.js, the jquery typing files will be downloaded.

• include: An array of library names whose typing files are needed, regardless of the inferring process. A sample value looks like: ["jquery", "commander"]. This can be used to implicitly add a library when auto discovery fails.

• exclude: an array of library names that should not be used, regardless of the inferring process. If a library name is put in this array, the corresponding .d.ts files wouldn't be used during editing session, even if they were already downloaded in the typings folder. This can fix the case when auto discovery falsely used wrong typing information for the project.

Common issues

The node_modules folder can contain thousands of JavaScript files and when this folder is included in the project as a source folder VS Code can run out of memory. To avoid this, make sure your tsconfig.json or jsconfig.json has either an explicit files array, or the node_modules folder in the exclude folder list (not the exclude library name list within typingOptions).