Entry Points

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Like we mentioned in the introduction, there are multiple ways to define the entry property in your webpack configuration. We will show you the ways you can configure the entry property, in addition to explaining why it may be useful to you.

Single Entry (Shorthand) Syntax

Usage: entry: string|Array<string>

webpack.config.js

const config = {
  entry: './path/to/my/entry/file.js'
};

module.exports = config;

The single entry syntax for the entry property is a shorthand for:

const config = {
  entry: {
    main: './path/to/my/entry/file.js'
  }
};
What happens when you pass an array to entry? Passing an array of file paths to the entry property creates what is known as a "multi-main entry". This is useful when you would like to inject multiple dependent files together and graph their dependencies into one "chunk".

This is a great choice when you are looking to quickly setup a webpack configuration for an application or tool with one entry point (IE: a library). However, there is not much flexibility in extending or scaling your configuration with this syntax.

Object Syntax

Usage: entry: {[entryChunkName: string]: string|Array<string>}

webpack.config.js

const config = {
  entry: {
    app: './src/app.js',
    vendors: './src/vendors.js'
  }
};

The object syntax is more verbose. However, this is the most scalable way of defining entry/entries in your application.

"Scalable webpack configurations" are ones that can be reused and combined with other partial configurations. This is a popular technique used to separate concerns by environment, build target and runtime. They are then merged using specialized tools like webpack-merge.

Scenarios

Below is a list of entry configurations and their real-world use cases:

Separate App and Vendor Entries

webpack.config.js

const config = {
  entry: {
    app: './src/app.js',
    vendors: './src/vendors.js'
  }
};

What does this do? At face value this tells webpack to create dependency graphs starting at both app.js and vendors.js. These graphs are completely separate and independent of each other (there will be a webpack bootstrap in each bundle). This is commonly seen with single page applications which have only one entry point (excluding vendors).

Why? This setup allows you to leverage CommonsChunkPlugin and extract any vendor references from your app bundle into your vendor bundle, replacing them with __webpack_require__() calls. If there is no vendor code in your application bundle, then you can achieve a common pattern in webpack known as long-term vendor-caching.

Consider removing this scenario in favor of the DllPlugin, which provides a better vendor-splitting.

Multi Page Application

webpack.config.js

const config = {
  entry: {
    pageOne: './src/pageOne/index.js',
    pageTwo: './src/pageTwo/index.js',
    pageThree: './src/pageThree/index.js'
  }
};

What does this do? We are telling webpack that we would like 3 separate dependency graphs (like the above example).

Why? In a multi-page application, the server is going to fetch a new HTML document for you. The page reloads this new document and assets are redownloaded. However, this gives us the unique opportunity to do multiple things:

  • Use CommonsChunkPlugin to create bundles of shared application code between each page. Multi-page applications that reuse a lot of code/modules between entry points can greatly benefit from these techniques, as the amount of entry points increase.
As a rule of thumb: for each HTML document use exactly one entry point.

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