Extending outdated TypeScript package declarations

Published November 2, 2023Last updated February 4, 20241 min read

Extending package declarations locally is one of the options for outdated package typings.

Create a declaration file .d.ts (e.g., handlebars.d.ts), and put it inside the src directories.

Find the exact name of the package namespace inside the node_modules types file (e.g. handlebars/types/index.d.ts).

Extend the found namespace with your needed properties, like classes, functions, etc.

// handlebars.d.ts
declare namespace Handlebars {
export class JavaScriptCompiler {
public nameLookup(parent: string, name: string, type: string): string | string[];
export function doSomething(name: string): void;
// ...