The tsconfig option lib is used to specify a set of bundled library declaration files that describe the target runtime environment for a TypeScript project. Essentially, it allows developers to define which built-in API declarations (like Math, DOM APIs, etc.) should be included during the compilation process. This is particularly useful for ensuring that your TypeScript code is compatible with the runtime environment it will be executed in, whether that's a specific version of ECMAScript, a browser environment, or Node.js.
For example, if your target environment supports ES5, you might specify "lib": ["es5"] in your tsconfig.json. This tells the TypeScript compiler to include type definitions for ES5, ensuring that your code is checked against the correct type definitions for that environment. If you're using features from ES2015 (ES6) like Promises, you would need to include "es2015.promise" in the lib array to inform the TypeScript compiler that these features will be available at runtime, possibly through polyfills.
The default value of the lib option is derived from the target option, which sets the JavaScript language version for the emitted JavaScript. If no lib option is specified, TypeScript includes default libraries based on the specified target. For instance, targeting "es5" would automatically include type definitions for ES5 and DOM APIs. However, develop...
