Dependency Management

es6 modules

commonjs

amd

require with expression

A context is created if your request contains expressions, so the exact module is not known on compile time.

Example, given we have the following folder structure including .ejs files:

example_directory
│
└───template
│   │   table.ejs
│   │   table-row.ejs
│   │
│   └───directory
│       │   another.ejs

When following require() call is evaluated:

require('./template/' + name + '.ejs');

webpack parses the require() call and extracts some information:

Directory: ./template
Regular expression: /^.*\.ejs$/

context module

A context module is generated. It contains references to all modules in that directory that can be required with a request matching the regular expression. The context module contains a map which translates requests to module ids.

Example map:

{
  "./table.ejs": 42,
  "./table-row.ejs": 43,
  "./directory/another.ejs": 44
}

The context module also contains some runtime logic to access the map.

This means dynamic requires are supported but will cause all matching modules to be included in the bundle.

require.context

You can create your own context with the require.context() function.

It allows you to pass in a directory to search, a flag indicating whether subdirectories should be searched too, and a regular expression to match files against.

webpack parses for require.context() in the code while building.

The syntax is as follows:

require.context(directory, useSubdirectories = true, regExp = /^\.\/.*$/, mode = 'sync');

Examples:

require.context('./test', false, /\.test\.js$/);
// a context with files from the test directory that can be required with a request ending with `.test.js`.

require.context('../', true, /\.stories\.js$/);
// a context with all files in the parent folder and descending folders ending with `.stories.js`.

The arguments passed to require.context must be literals!

context module API

A context module exports a (require) function that takes one argument: the request.

The exported function has 3 properties: resolve, keys, id.

• resolve is a function and returns the module id of the parsed request.
• keys is a function that returns an array of all possible requests that the context module can handle.

This can be useful if you want to require all files in a directory or matching a pattern, Example:

function importAll (r) {
  r.keys().forEach(r);
}

importAll(require.context('../components/', true, /\.js$/));

const cache = {};

function importAll (r) {
  r.keys().forEach(key => cache[key] = r(key));
}

importAll(require.context('../components/', true, /\.js$/));
// At build-time cache will be populated with all required modules.

• id is the module id of the context module. This may be useful for module.hot.accept.