TypeScript with JavaScript Libraries

You do not need to abandon JavaScript to use TypeScript. ## Using JS files in TS project You can mix: - .ts files - .js files TypeScript understands JS. ## Installing type definitions Many JS libraries provide types via DefinitelyTyped. Example: ```bash npm install lodash npm install --save-dev @types/lodash ``` ## Using the library ```ts import _ from "lodash"; const nums = [1, 2, 3]; const doubled = _.map(nums, n => n * 2); ``` Now you get: - autocomplete - type checking ## Gradual migration idea Start with: - allowJs: true in tsconfig - convert files slowly from .js to .ts ## Remember - TypeScript works with JS ecosystem - types give safety on top of JS libraries - migration can be gradual