How to use publicPath path in Webpack

This time I will show you how to use the publicPath path in Webpack, and what are the precautions for using the publicPath path in Webpack. The following is a practical case, let's take a look.

output

The output option specifies the location of the webpack output. The more important and often used ones are path and publicPath

output.path

Default value: process.cwd()

output.path just indicates the output directory, corresponding to an absolute path, such as usually in a project The following configuration will be made:

output: {
 path: path.resolve(dirname, '../dist'),
}

output.publicPath

Default value: empty

String

The publicPath is specified in the official documentation The explanation is that

webpack provides a very useful configuration that can help you specify a base path for all resources in the project, which is called the public path (publicPath).

There is no clear explanation on how to apply this path...

In fact, the basic path of all resources mentioned here refers to

referencescss, js, img in the project A basic path when waiting for resources. This basic path must be used in conjunction with the path specified in the specific resource. Therefore, in fact, the access path of the packaged resource can be expressed by the following formula:

Final access path of static resources = output.publicPath Resource loader or plug-in configuration path

For example

output.publicPath = '/dist/'
// image
options: {
 name: 'img/[name].[ext]?[hash]'
}
// 最终图片的访问路径为
output.publicPath + 'img/[name].[ext]?[hash]' = '/dist/img/[name].[ext]?[hash]'
// js output.filename
output: {
 filename: '[name].js'
}
// 最终js的访问路径为
output.publicPath + '[name].js' = '/dist/[name].js'
// extract-text-webpack-plugin css
new ExtractTextPlugin({
 filename: 'style.[chunkhash].css'
})
// 最终css的访问路径为
output.publicPath + 'style.[chunkhash].css' = '/dist/style.[chunkhash].css'

This final static resource access path can be seen in the HTML obtained after packaging using html-webpack-plugin. Therefore, after publicPath is set to a relative path, the relative path is relative to index.html after build. For example, if publicPath: './dist/' is set, the reference path of packaged js is ./dist/main.js. But there is a problem here. Relative paths are OK when accessing local, but if static resources are hosted on CDN, the access path obviously cannot use relative paths. However, if publicPath is set to /, the access path after packaging is localhost:8080/ dist/main.js, cannot be accessed locally

So here you need to manually change the publicPath when going online. It feels not very convenient, but I don’t know how to solve it...

Generally, publicPath should be End with '/', and the configuration of other loaders or plug-ins should not start with '/'

publicPath in webpack-dev-server

Click to view the official documentation Introduction to devServer.publicPath

In the development stage, we use devServer to start a development server for development. A publicPath will also be configured here. The packaged files under the publicPath path here can be accessed in the browser. Static resources still use output.publicPath.

The content packaged by webpack-dev-server is placed in memory. The external root directory of these packaged resources is publicPath. In other words, here we set the location where the packaged resources are stored.

For example:

// 假设devServer的publicPath为
const publicPath = '/dist/'
// 则启动devServer后index.html的位置为
const htmlPath = `${pablicPath}index.html`
// 包的位置
cosnt mainJsPath = `${pablicPath}main.js`

The above can be accessed directly through http://lcoalhost:8080/dist/main.js.

By accessing http://localhost:8080/webpack-dev-server, you can get the resource access path after devServer is started. As shown in the figure, click on the static resource to see that the access path of the static resource is http: //localhost:8080${publicPath}index.html

##html-webpack-plugin This plug-in is used to add css and js to html templates, where template and filename will be affected by the path. From the source code, we can see the

template

effect : used to define the path of the template file

Source code:

Copy code

The code is as follows: this.options.template = this.getFullTemplatePath(this .options.template, compiler.context);

Therefore, template will only be recognized if it is defined in the context of webpack. The default value of webpack context is process.cwd(), which is the file in which the node command is run. Absolute path to the folder

filename

Function: The output HTML file name, the default is index.html, can be directly configured with subdirectories

Source code:

Copy code The code is as follows:

this.options.filename = path.relative(compiler.options.output.path, filename);

So the path of filename is relative to output.path, and in webpack-dev- In server, it is relative to the publicPath configured in webpack-dev-server.

If the publicPath of webpack-dev-server is inconsistent with output.publicPath, using html-webpack-plugin may cause failure to reference static resources, because static resources are still referenced by output.publicPath in devServer, and webpack The resource access paths provided by -dev-server are inconsistent and cannot be accessed normally.

There is one exception, that is, output.publicPath is a relative path, and local resources can be accessed at this time.

So in general, it is necessary to ensure that the publicPath in devServer is consistent with output.publicPath.

Finally

About the path in webpack, that’s all. In the process of studying the webpack path, I saw some information about the path. The fragmentary knowledge is as follows:

The meaning of slash/

/ in the configuration represents the url root path, such as http://localhost:8080/dist/js/test.js ://localhost:8080/

devServer.publicPath & devServer.contentBase

1. ##devServer.contentBase tells the server where to serve content from. Only required if you want to serve static files.

2. devServer.publicPath will be used to determine where the bundle should be served from, and this option takes precedence.

Path in node

1. dirname: always returns the absolute path of the folder where the executed js is located

2. filename: always returns the absolute path of the executed js

3. process.cwd(): always returns the location where the node command is run Absolute path of the folder

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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