The first step to optimising your webpack build speed, is to know where to focus your attention.
This plugin measures your webpack build speed, giving an output like this:
## Install
```bash
npm install --save-dev speed-measure-webpack-plugin
```
or
```bash
yarn add -D speed-measure-webpack-plugin
```
## Requirements
SMP requires at least **Node v6**. But otherwise, accepts **all webpack** versions (1, 2, 3, and 4).
## Usage
Change your webpack config from
```javascript
const webpackConfig = {
plugins: [new MyPlugin(), new MyOtherPlugin()],
};
```
to
```javascript
const SpeedMeasurePlugin = require("speed-measure-webpack-plugin");
const smp = new SpeedMeasurePlugin();
const webpackConfig = smp.wrap({
plugins: [new MyPlugin(), new MyOtherPlugin()],
});
```
and you're done! SMP will now be printing timing output to the console by default.
Check out the [examples folder](/examples) for some more examples.
## Options
Pass these into the constructor, as an object:
```javascript
const smp = new SpeedMeasurePlugin(options);
```
### `options.disable`
Type: `Boolean`
Default: `false`
If truthy, this plugin does nothing at all.
`{ disable: !process.env.MEASURE }` allows opt-in measurements with `MEASURE=true npm run build`.
### `options.outputFormat`
Type: `String|Function`
Default: `"human"`
Determines in what format this plugin prints its measurements
- `"json"` - produces a JSON blob
- `"human"` - produces a human readable output
- `"humanVerbose"` - produces a more verbose version of the human readable output
- If a function, it will call the function with the JSON blob, and output the response
### `options.outputTarget`
Type: `String|Function`
Default: `console.log`
- If a string, it specifies the path to a file to output to.
- If a function, it will call the function with the output as the first parameter
### `options.pluginNames`
Type: `Object`
Default: `{}`
By default, SMP derives plugin names through `plugin.constructor.name`. For some
plugins this doesn't work (or you may want to override this default). This option
takes an object of `pluginName: PluginConstructor`, e.g.
```javascript
const uglify = new UglifyJSPlugin();
const smp = new SpeedMeasurePlugin({
pluginNames: {
customUglifyName: uglify,
},
});
const webpackConfig = smp.wrap({
plugins: [uglify],
});
```
### `options.loaderTopFiles`
Type: `Number`
Default: `0`
You can configure SMP to include the files that take the most time per loader, when using `outputFormat: 'humanVerbose'`. E.g., to show the top 10 files per loader:
```javascript
const smp = new SpeedMeasurePlugin({
outputFormat: "humanVerbose",
loaderTopFiles: 10,
});
```
### `options.compareLoadersBuild`
Type: `Object`
Default: `{}`
This option gives you a comparison over time of the module count and time spent, per loader. This option provides more data when `outputFormat: "humanVerbose"`.
Given a required `filePath` to store the build information, this option allows you to compare differences to your codebase over time. E.g.
```javascript
const smp = new SpeedMeasurePlugin({
compareLoadersBuild: {
filePath: "./buildInfo.json",
},
});
```
### `options.granularLoaderData` _(experimental)_
Type: `Boolean`
Default: `false`
By default, SMP measures loaders in groups. If truthy, this plugin will give per-loader timing information.
This flag is _experimental_. Some loaders will have inaccurate results:
- loaders using separate processes (e.g. `thread-loader`)
- loaders emitting file output (e.g. `file-loader`)
We will find solutions to these issues before removing the _(experimental)_ flag on this option.
## FAQ
### What does general output time mean?
This tends to be down to webpack reading in from the file-system, but in general it's anything outside of what SMP can actually measure.
### What does modules without loaders mean?
It means vanilla JS files, which webpack can handle out of the box.
## Contributing
Contributors are welcome! π
Please check out the [CONTRIBUTING.md](./CONTRIBUTING.md).
## Migrating
SMP follows [semver](https://semver.org/). If upgrading a major version, you can consult [the migration guide](./migration.md).
## License
[MIT](/LICENSE)
## Contributors β¨
Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):
