# tslib

This is a runtime library for [TypeScript](http://www.typescriptlang.org/) 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`.

# Installing

For the latest stable version, run:

## npm

```sh
# TypeScript 3.9.2 or later
npm install tslib

# TypeScript 3.8.4 or earlier
npm install tslib@^1

# TypeScript 2.3.2 or earlier
npm install tslib@1.6.1
```

## yarn

```sh
# TypeScript 3.9.2 or later
yarn add tslib

# TypeScript 3.8.4 or earlier
yarn add tslib@^1

# TypeScript 2.3.2 or earlier
yarn add tslib@1.6.1
```

## bower

```sh
# TypeScript 3.9.2 or later
bower install tslib

# TypeScript 3.8.4 or earlier
bower install tslib@^1

# TypeScript 2.3.2 or earlier
bower install tslib@1.6.1
```

## JSPM

```sh
# TypeScript 3.9.2 or later
jspm install tslib

# TypeScript 3.8.4 or earlier
jspm install tslib@^1

# 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:

```json
{
    "compilerOptions": {
        "importHelpers": true
    }
}
```

#### For bower and JSPM users

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@2.x.y/tslib.d.ts"]
        }
    }
}
```


# Contribute

There are many ways to [contribute](https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md) to TypeScript.

* [Submit bugs](https://github.com/Microsoft/TypeScript/issues) and help us verify fixes as they are checked in.
* Review the [source code changes](https://github.com/Microsoft/TypeScript/pulls).
* Engage with other TypeScript users and developers on [StackOverflow](http://stackoverflow.com/questions/tagged/typescript).
* Join the [#typescript](http://twitter.com/#!/search/realtime/%23typescript) discussion on Twitter.
* [Contribute bug fixes](https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md).

# Documentation

* [Quick tutorial](http://www.typescriptlang.org/Tutorial)
* [Programming handbook](http://www.typescriptlang.org/Handbook)
* [Homepage](http://www.typescriptlang.org/)
