This is a runtime library for TypeScript that contains all of the TypeScript helper functions.
This library is primarily used by the --importHelpers flag in TypeScript.
When using --importHelpers, a module that uses helper functions like __extends and __assign in the following emitted file:
```ts var __assign = (this && this.__assign) || Object.assign || function(t) { for (var s, i = 1, n = arguments.length; i < n; i++) { s = arguments[i]; for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p)) t[p] = s[p]; } return t; }; exports.x = {}; exports.y = __assign({}, exports.x);
```
will instead be emitted as something like the following:
ts
var tslib_1 = require("tslib");
exports.x = {};
exports.y = tslib_1.__assign({}, exports.x);
Because this can avoid duplicate declarations of things like __extends, __assign, etc., this means delivering users smaller files on average, as well as less runtime overhead.
For optimized bundles with TypeScript, you should absolutely consider using tslib and --importHelpers.
For the latest stable version, run:
```sh
npm install tslib
npm install tslib@1.6.1 ```
```sh
yarn add tslib
yarn add tslib@1.6.1 ```
```sh
bower install tslib
bower install tslib@1.6.1 ```
```sh
jspm install tslib
jspm install tslib@1.6.1 ```
Set the importHelpers compiler option on the command line:
tsc --importHelpers file.ts
or in your tsconfig.json:
json
{
"compilerOptions": {
"importHelpers": true
}
}
You will need to add a paths mapping for tslib, e.g. For Bower users:
json
{
"compilerOptions": {
"module": "amd",
"importHelpers": true,
"baseUrl": "./",
"paths": {
"tslib" : ["bower_components/tslib/tslib.d.ts"]
}
}
}
For JSPM users:
json
{
"compilerOptions": {
"module": "system",
"importHelpers": true,
"baseUrl": "./",
"paths": {
"tslib" : ["jspm_packages/npm/tslib@1.[version].0/tslib.d.ts"]
}
}
}
There are many ways to contribute to TypeScript.