Configuration Types
Besides exporting a single configuration object, there are a few more ways that cover other needs as well.
Exporting a Function
Eventually you will find the need to disambiguate in your webpack.config.js between development and production builds. There are multiple ways to do that. One option is to export a function from your webpack configuration instead of exporting an object. The function will be invoked with two arguments:
- An environment as the first parameter. See the environment options CLI documentation for syntax examples.
- An options map (
argv) as the second parameter. This describes the options passed to webpack, with keys such asoutput-pathandmode.
-module.exports = {
+module.exports = function(env, argv) {
+ return {
+ mode: env.production ? 'production' : 'development',
+ devtool: env.production ? 'source-map' : 'eval',
plugins: [
new TerserPlugin({
terserOptions: {
+ compress: argv.mode === 'production' // only if `--mode production` was passed
}
})
]
+ };
};Exporting a Promise
webpack will run the function exported by the configuration file and wait for a Promise to be returned. Handy when you need to asynchronously load configuration variables.
module.exports = () => {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve({
entry: './app.js',
/* ... */
});
}, 5000);
});
};Exporting multiple configurations
Instead of exporting a single configuration object/function, you may export multiple configurations (multiple functions are supported since webpack 3.1.0). When running webpack, all configurations are built. For instance, this is useful for bundling a library for multiple targets such as AMD and CommonJS:
module.exports = [
{
output: {
filename: './dist-amd.js',
libraryTarget: 'amd',
},
name: 'amd',
entry: './app.js',
mode: 'production',
},
{
output: {
filename: './dist-commonjs.js',
libraryTarget: 'commonjs',
},
name: 'commonjs',
entry: './app.js',
mode: 'production',
},
];parallelism
In case you export multiple configurations, you can use parallelism option on the configuration array to specify the maximum number of compilers that will compile in parallel.
- Type:
number - Available: 5.22.0+
webpack.config.js
module.exports = [
{
//config-1
},
{
//config-2
},
];
module.exports.parallelism = 1;