How to Define Global Variable In Webpack?

In webpack, global variables can be defined using the ProvidePlugin. This plugin allows you to specify a variable name and its corresponding module or package that should be globally available in your project. The syntax for defining a global variable using ProvidePlugin is as follows:

1
2
3
4

new webpack.ProvidePlugin({
  $: 'jquery',
  _: 'lodash'
})

In this example, we are defining two global variables: $ and _, which will be resolved to the 'jquery' and 'lodash' modules respectively. Once you have added the ProvidePlugin configuration to your webpack configuration file, you can use these global variables in any module without having to explicitly import them. This can be especially useful for libraries or utilities that you use frequently across your project.

How to share global variables across multiple entry points in webpack?

One way to share global variables across multiple entry points in webpack is to use the ProvidePlugin or DefinePlugin from webpack.

1. ProvidePlugin: You can use the ProvidePlugin to automatically load certain modules when you use a specific identifier. This can be useful for sharing global variables across multiple entry points.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12

// webpack.config.js
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.ProvidePlugin({
      $: 'jquery',
      jQuery: 'jquery',
      'window.jQuery': 'jquery'
    })
  ]
};

1. DefinePlugin: You can use the DefinePlugin to define global variables that can be accessed in your code.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10

// webpack.config.js
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.DefinePlugin({
      GLOBAL_VARIABLE: JSON.stringify('some value')
    })
  ]
};

Another approach is to use the externals configuration option in webpack to have a shared module that exports your global variables.

1
2
3
4
5
6
7
8

// globals.js
export const myGlobalVariable = 'some value';

// entry-point-1.js
import { myGlobalVariable } from './globals';

// entry-point-2.js
import { myGlobalVariable } from './globals';

Then in the webpack configuration file, you can specify the shared module as an external dependency.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10

// webpack.config.js
module.exports = {
  externals: {
    './globals': {
      commonjs: './globals',
      amd: './globals',
      root: 'myGlobal'
    }
  }
};

What is the impact of global variables on webpack's tree-shaking capabilities?

Global variables can have a significant impact on webpack's tree-shaking capabilities because they can make it harder for webpack to determine which code is actually being used and which code can be safely removed during the optimization process.

When global variables are used, webpack may not be able to accurately analyze and trace the dependencies of the code, leading to potential issues with tree-shaking. This can result in larger bundle sizes and decreased performance as unused code is not properly eliminated.

To improve tree-shaking capabilities, it is recommended to minimize the use of global variables and instead utilize ES6 modules or other modern practices that allow for better static analysis and optimization by webpack. Additionally, ensuring that code is properly written and structured can also help webpack accurately determine what code can be safely removed during the bundling process.

What is the difference between defining global variables in development and production builds in webpack?

In development builds, global variables can be defined using the webpack.DefinePlugin to provide specific values in the source code during development. This can be helpful for debugging and testing purposes.

In production builds, global variables can also be defined using the webpack.DefinePlugin, but with different values to optimize the code for production. This may include setting different configuration values or disabling certain features that are not necessary in a production environment.

Overall, the difference lies in the values that are assigned to global variables in development and production builds, as well as the optimizations and settings that are applied for each environment.