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:

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:

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.

Installing

For the latest stable version, run:

npm

# TypeScript 2.3.3 or later
npm install tslib

# TypeScript 2.3.2 or earlier
npm install tslib@1.6.1

yarn

# TypeScript 2.3.3 or later
yarn add tslib

# TypeScript 2.3.2 or earlier
yarn add tslib@1.6.1

bower

# TypeScript 2.3.3 or later
bower install tslib

# TypeScript 2.3.2 or earlier
bower install tslib@1.6.1

JSPM

# TypeScript 2.3.3 or later
jspm install tslib

# TypeScript 2.3.2 or earlier
jspm install tslib@1.6.1

Usage

Set the importHelpers compiler option on the command line:

tsc --importHelpers file.ts

or in your tsconfig.json:

{
    "compilerOptions": {
        "importHelpers": true
    }
}

For bower and JSPM users

You will need to add a paths mapping for tslib, e.g. For Bower users:

{
    "compilerOptions": {
        "module": "amd",
        "importHelpers": true,
        "baseUrl": "./",
        "paths": {
            "tslib" : ["bower_components/tslib/tslib.d.ts"]
        }
    }
}

For JSPM users:

{
    "compilerOptions": {
        "module": "system",
        "importHelpers": true,
        "baseUrl": "./",
        "paths": {
            "tslib" : ["jspm_packages/npm/tslib@1.[version].0/tslib.d.ts"]
        }
    }
}

Contribute

There are many ways to contribute to TypeScript.

Submit bugs and help us verify fixes as they are checked in.
Review the source code changes.
Engage with other TypeScript users and developers on StackOverflow.
Join the #typescript discussion on Twitter.
Contribute bug fixes.

README.md

tslib