# TypeScript loader for Webpack
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[](https://travis-ci.org/s-panferov/awesome-typescript-loader)
See also:
1. [tygen](https://github.com/s-panferov/tygen) — TypeScript documentation generator.
## Installation
```
npm install awesome-typescript-loader --save-dev
```
## Performance issues
Please note that ATL works **the same way as a TypeScript compiler** as much as possible. So please be careful with your `files`/`exclude`/`include` sections.
**ADVICE**: Turn on `useCache` option.
**ADVICE**: Typically you want your `files` section to include only entry points.
**ADVICE**: The loader works faster if you use `isolatedModules` or `forceIsolatedModules` options.
**ADVICE**: The loader works faster if you will use `reportFiles` to restrict
checking scope.
**ADVICE**: Use the loader together with [hard-source-webpack-plugin](https://github.com/mzgoddard/hard-source-webpack-plugin)
The world is changing, other solutions are evolving and ATL may work **slower**
for [some workloads](https://github.com/s-panferov/awesome-typescript-loader/issues/497). Feel free to try [`ts-loader`](https://github.com/TypeStrong/ts-loader) with [`HappyPack` ](https://github.com/amireh/happypack) or [`thread-loader`](https://webpack.js.org/loaders/thread-loader/) and [hard-source-webpack-plugin](https://github.com/mzgoddard/hard-source-webpack-plugin).
## Differences between [`ts-loader`](https://github.com/TypeStrong/ts-loader)
`awesome-typescript-loader` loader was created mostly to speed-up compilation in my own projects.
Some of them are quite big and I wanted to have full control on how my files are compiled. There are two major points:
1) atl has first-class integration with Babel and enables caching possibilities. This can be useful for those who use Typescript with Babel.
When `useBabel` and `useCache` flags are enabled, typescript's emit will be transpiled with Babel and cached.
So next time if source file (+environment) has the same checksum we can totally skip typescript's and babel's transpiling.
This significantly reduces build time in this scenario.
2) atl is able to fork type-checker and emitter to a separate process, which also speeds-up some development scenarios (e.g. react with react-hot-loader)
So your webpack compilation will end earlier and you can explore compiled version in your browser while your files are typechecked.
## Configuration
1. Add `.ts` as a resolvable extension.
2. Configure all files with a `.ts` extension to be handled by `awesome-typescript-loader`.
**webpack.config.js**
```javascript
// `CheckerPlugin` is optional. Use it if you want async error reporting.
// We need this plugin to detect a `--watch` mode. It may be removed later
// after https://github.com/webpack/webpack/issues/3460 will be resolved.
const { CheckerPlugin } = require('awesome-typescript-loader')
module.exports = {
// Currently we need to add '.ts' to the resolve.extensions array.
resolve: {
extensions: ['.ts', '.tsx', '.js', '.jsx']
},
// Source maps support ('inline-source-map' also works)
devtool: 'source-map',
// Add the loader for .ts files.
module: {
rules: [
{
test: /\.tsx?$/,
loader: 'awesome-typescript-loader'
}
]
},
plugins: [
new CheckerPlugin()
]
};
```
After that, you will be able to build TypeScript files with webpack.
## NodeJS versions
**The loader supports NodeJS 4 and newer.**
## tsconfig.json
You can use the tsconfig.json file to configure your compiler and loader:
```
{
"compilerOptions": {
"noImplicitAny": true,
"removeComments": true
},
"awesomeTypescriptLoaderOptions": {
/* ... */
}
}
```
## Supported TypeScript
`awesome-typescript-loader@2.x` aims to support only `typescript@2.x` and `webpack@2x`, if you need old compilers please use
`1.x` or `0.x` versions.
## Advanced path resolution in TypeScript 2.0
If you want to use new `paths` and `baseUrl` feature of TS 2.0 please include `TsConfigPathsPlugin`.
This feature is available only for `webpack@2.1`.
```
const { TsConfigPathsPlugin } = require('awesome-typescript-loader');
resolve: {
plugins: [
new TsConfigPathsPlugin(/* { configFileName, compiler } */)
]
}
```
## Loader options
### silent *(boolean) (default=false)*
No logging from the checker. Please note that this option disables async error reporting because
this option bans `console.log()` usage.
### compiler *(string) (default='typescript')*
Allows use of TypeScript compilers other than the official one. Must be
set to the NPM name of the compiler, e.g. *ntypescript* or the path to a package folder.
Note that the compiler must be installed in **your** project. You can also use
nightly versions.
### useTranspileModule (boolean) (default=false)*
Use fast `transpileModule` emit mode. Disables automatically when you set compilerOption `declaration: true` ([reference](https://www.typescriptlang.org/docs/handbook/compiler-options.html)).
### instance *(string) (default='at-loader')*
Allows the use of several TypeScript compilers with different settings in one app. Override `instance` to initialize another instance.
### configFileName *(string) (default='tsconfig.json')*
Specifies the path to a TS config file. This is useful when you have multiple config files. This setting is useless *inside* a TS config file.
### transpileOnly *(boolean)*
Use this setting to disable type checking, enabling this will nullify the `CheckerPlugin` usage in your webpack configuration.
### errorsAsWarnings *(boolean)*
Emit all typescript errors as warnings.
### forceIsolatedModules *(boolean)*
Use this setting to disable dependent module recompilation.
### ignoreDiagnostics *(number[]) (default=[])*
You can squelch certain TypeScript errors by specifying an array of [diagnostic codes](https://github.com/Microsoft/TypeScript/blob/master/src/compiler/diagnosticMessages.json) to ignore.
For example, you can transpile [stage 1 properties](https://github.com/jeffmo/es-class-fields-and-static-properties) from `*.js` using `"ignoreDiagnostics": [8014]`.
### useBabel *(boolean) (default=false)*
Invoke Babel to transpile files. Useful with ES6 target. Please see `useCache` option
which can improve warm-up time.
If you're using `babelOptions`, anything in `.babelrc` will take precedence. This breaks expected usage for scenarios where you need two sets of Babel configs (example: one for Webpack, one for your build tools).
You may want to `"babelrc": false` to disable `.babelrc` if you don't want it:
```json
{
"useBabel": true,
"babelOptions": {
"babelrc": false, /* Important line */
"presets": [
["@babel/preset-env", { "targets": "last 2 versions, ie 11", "modules": false }]
]
},
"babelCore": "@babel/core", // needed for Babel v7
}
```
### babelCore *(string) (default=undefined)*
Override the path used to find `babel-core`. Useful if `node_modules` is installed in a non-standard place or webpack is being invoked from a directory not at the root of the project.
For Babel 7, this should be set to `"@babel/core"`.
### babelOptions *(object) (default=null)*
Use this option to pass some options to Babel (e.g. presets). Please note that
[`.babelrc` file](https://babeljs.io/docs/usage/babelrc/) is more universal way to do this.
### useCache *(boolean) (default=false)*
Use internal file cache. This is useful with Babel, when processing takes a long time to complete. Improves warm-up time.
### usePrecompiledFiles *(boolean) (default=false)*
Use pre-compiled files if any. Files must be named as `{filename}.js` and `{filename}.map`.
### cacheDirectory *(string) (default='.awcache')*
Directory where cache is stored.
### reportFiles *(string[])*
Specify [globs](https://github.com/isaacs/minimatch) to report file diagnostics. ALL OTHER ERRORS WILL NOT BE REPORTED. Example:
```
reportFiles: [
"src/**/*.{ts,tsx}"
]
```
### getCustomTransformers *(string | ((program: ts.Program) => ts.CustomTransformers | undefined)) (default=undefined)*
Provide custom transformers, TypeScript 2.4.1+. Example:
```js
const styledComponentsTransformer = require('typescript-plugin-styled-components').default;
const keysTransformer = require('ts-transformer-keys/transformer').default;
// ...
rules: [
{
test: /\.tsx?$/,
loader: 'awesome-typescript-loader',
options: {
// ... other loader's options
getCustomTransformers: program => ({
before: [
styledComponentsTransformer(),
keysTransformer(program)
]
})
}
}
]
```
## Compiler options
You can pass compiler options inside the loader query string or in a TS config file.