Generate typings from JavaScript with TypeScript 3.7
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TypeScript 3.7 enables the creation of declaration files from JavaScript, aiding library authors in bootstraping definitions and allowing comparisons with manually typed definitions. However, limitations include the need for specific module flags and potential interference of exported classnames with module names. The document illustrates the use of the TypeScript compiler with examples of code generation and the resultant declaration files.
Generate typings from JavaScript with TypeScript 3.7
- 1. TypeScript 3.7 Language Compiler Create declarations from JavaScript
- 2. Benefits • JavaScript library authors can bootstrap definition files • Automatically generated definitions can be compared with manually typed definitions (using third-party tools like TSEvolve) Limitations • --module flag must be „amd“ or „system“ (doesn‘t work with „esnext“) to use --out • Exports get wrapped in modules • Exported classnames can interfere with module name 2019/12/17
- 3. Demo tsc src/Point.js --allowJs --declaration --out dist/Point.js --module system • --allowJs combined with --declaration (available with TypeScript 3.7) 2019/12/17
- 4. ./src/Point.js export class Point { constructor(x, y) { this.x = x; this.y = y; } equals(point) { return this.x === point.x && this.y === point.y; } } 2019/12/17
- 5. ./dist/Point.d.ts declare module "Point" { export class Point { constructor(x: any, y: any); x: any; y: any; equals(point: any): boolean; } } 2019/12/17