shimming modules

Not all JS files can be used directly with webpack. The file might be in an unsupported module format, or not even in any module format.

Webpack provides several loaders to make these files work with webpack.

The examples on this use require to keep them short. You will usually want to configure them in your webpack config. See Using loaders.

Importing

If a file has dependencies that are not imported via require(), you will need to use one of these loaders.

imports-loader

The imports loader allows you to use modules that depend on specific global variables.

This is useful for third-party modules that rely on global variables like $ or this being the window object. The imports loader can add the necessary require('whatever') calls, so those modules work with webpack.

Examples:

file.js expects a global variable $ and you have a module jquery that should be used.

require("imports-loader?$=jquery!./file.js")

file.js expects its configuration on a global variable xConfig and you want it to be {value:123}.

require("imports-loader?xConfig=>{value:123}!./file.js")

file.js expect that this is the global context.

require("imports-loader?this=>window!./file.js") or require("imports-loader?this=>global!./file.js")

plugin ProvidePlugin

This plugin makes a module available as a variable in every module. The module is required only if you use the variable.

Example: Make $ and jQuery available in every module without writing require("jquery").

new webpack.ProvidePlugin({
	$: "jquery",
	jQuery: "jquery",
	"window.jQuery": "jquery"
})

Exporting

The file doesn't export its value.

exports-loader

This loader exports variables from inside the file.

Examples:

The file sets a variable in the global context with var XModule = ....

var XModule = require("exports-loader?XModule!./file.js")

The file sets multiple variables in the global context with var XParser, Minimizer.

var XModule = require("exports-loader?Parser=XParser&Minimizer!./file.js"); XModule.Parser; XModule.Minimizer

The file sets a global variable with XModule = ....

require("imports-loader?XModule=>undefined!exports-loader?XModule!./file.js") (import to not leak to the global context)

The file sets a property on window window.XModule = ....

require("imports-loader?window=>{}!exports-loader?window.XModule!./file.js")

Fixing broken module styles

Some files use a module style wrong. You may want to fix this by teaching webpack to not use this style.

Disable some module styles

Examples:

Broken AMD

require("imports-loader?define=>false!./file.js")

Broken CommonJs

require("imports-loader?require=>false!./file.js")

configuration option module.noParse

This disables parsing by webpack. Therefore you cannot use dependencies. This may be useful for prepackaged libraries.

Example:

{
	module: {
		noParse: [
			/XModule[\\\/]file\.js$/,
			path.join(__dirname, "web_modules", "XModule2")
		]
	}
}

Note: exports and module are still available and usable. You may want to undefine them with the imports-loader.

script-loader

This loader evaluates code in the global context, just like you would add the code into a script tag. In this mode every normal library should work. require, module, etc. are undefined.

Note: The file is added as string to the bundle. It is not minimized by webpack, so use a minimized version. There is also no dev tool support for libraries added by this loader.

Exposing

There are cases where you want a module to export itself to the global context.

Don't do this unless you really need this. (Better use the ProvidePlugin)

expose-loader

This loader exposes the exports to a module to the global context.

Example:

Expose file.js as XModule to the global context

require("expose-loader?XModule!./file.js")

Another Example:

   require('expose-loader?$!expose?jQuery!jquery');
   
   ...

   $(document).ready(function() {
   console.log("hey");
   })

By making jQuery available as a global namespace in our file containing jQuery code or the root file, you can use jQuery everywhere in your project. This works very well if you plan to implement Bootstrap(boot up the project) in your Webpack project.

Note: Using too much global name-spacing will make your app less efficient. If you are planning to use a lot of global namespaces, consider implementing something like Babel runtime to your project.

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Order of loaders

In rare cases when you have to apply more than one technique, you need to use the correct order of loaders:

inlined: expose-loader!imports-loader!export-loaders, configuration: expose before imports before exports.