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Detailed introduction to html-webpack-plugin
- 黄舟Original
- 2017-05-26 16:02:522699browse
Introduction
Recently, I used the html-webapck-plugin plug-in for the first time in a react project. The plug-in has two main functions:
For external resources introduced in the html file, such as Script and link dynamically add the hash after each compile to prevent the problem of referencing cached external files.
You can generate and create html entry files. For example, a single page can generate an html file entry and configure N html-webpack-plugins. Can generate N page entrances
With this plug-in, problems similar to the above can be easily solved in the project.
I use html-webpack-plugin in my project. Since I am not familiar with this plug-in, I encountered one or other problems during the development process. Let’s talk about this plug-in.
html-webpack-plugin
The basic function of the plug-in is to generate html files. The principle is very simple:
Insert the relevant entry thunk of the `entry` configuration in webpack and the css style extracted by `extract-text-webpack-plugin` into the `template` or `templateContent` configuration item provided by the plug-in Generate an html file based on the specified content. The specific insertion method is to insert the style `link` into the `head` element and `script` into `head` or `body`.
You can instantiate the plug-in without configuring any parameters, such as the following:
var HtmlWebpackPlugin = require('html-webpack-plugin')
webpackconfig = {
... plugins: [ new HtmlWebpackPlugin()
]}If the html-webpack-plugin plug-in does not configure any options, it will default to the html-webpack-plugin in webpack. Entry configuration All entry thunks and css styles extracted by extract-text-webpack-plugin are inserted into the location specified in the file. For example, the content of the html file generated above is as follows:
<!DOCTYPE html><html>
<head>
<meta charset="UTF-8">
<title>Webpack App</title>
<link href="index-af150e90583a89775c77.css" rel="stylesheet"></head>
<body>
<script type="text/javascript" src="common-26a14e7d42a7c7bbc4c2.js"></script>
<script type="text/javascript" src="index-af150e90583a89775c77.js"></script></body></html>Of course, you can use specific configuration items to customize some special needs. So what are the configuration items of the plug-in?
html-webpack-plugin configuration items
The plug-in provides many configuration items. The specific configuration items can be seen from the source code as follows:
this.options = _.extend({
template: path.join(__dirname, 'default_index.ejs'),
filename: 'index.html',
hash: false,
inject: true,
compile: true,
favicon: false,
minify: false,
cache: true,
showErrors: true,
chunks: 'all',
excludeChunks: [],
title: 'Webpack App',
xhtml: false
}, options);title: Generated html The title of the document. Configure this item, it will not replace the content of the title element in the specified template file, unless the template engine syntax is used in the html template file to obtain the configuration item value, as follows ejs template syntax form:
<title>{%= o.htmlWebpackPlugin.options.title %}</title>filename : The file name of the output file. The default is index.html. If not configured, it will be the file name. In addition, you can also specify the directory location for the output file (such as 'html/index.html')
Two additional comments about filename Points:
1. The html file directory configured by filename is relative to the webpackConfig.output.path path, not relative to the current project directory structure.
2. Specify that the link and script paths in the generated HTML file content are relative to the generation directory. When writing the path, please write the relative path to the generation directory.
template: The location of the local template file, supports loaders (such as handlebars, ejs, undersore, html, etc.), such as handlebars!src/index.hbs;
A few additional points about template :
1. When the template configuration item uses file-loader in the html file, the specified location cannot be found, causing the content of the generated html file to be not the expected content.
2. If the template file specified for template does not specify any loader, ejs-loader will be used by default. For example, template: './index.html', if no loader is specified for .html, use ejs-loader
templateContent: string|function, which can specify the content of the template and cannot coexist with template. When the configuration value is function, you can directly return an html string, or you can call it asynchronously to return an html string.
inject: Inject all static resources into template or templateContent. Different configuration values are injected at different locations.
1. true or body: All JavaScript resources are inserted at the bottom of the body element
2. head: All JavaScript resources are inserted into the head element
3. False: All static resources css and JavaScript are Will not be injected into the template file
favicon: Add a specific favicon path to the output html document. This is the same as the title configuration item, and its path value needs to be dynamically obtained in the template
hash: true |false, whether to add the unique hash value generated by webpack for each injected static resource. The hash form is as follows:
html 87bbc04a8ad365a43c97641db034ff782cacc6d41bbb37262a98f745aa00fbf0
chunks：允许插入到模板中的一些chunk，不配置此项默认会将entry中所有的thunk注入到模板中。在配置多个页面时，每个页面注入的thunk应该是不相同的，需要通过该配置为不同页面注入不同的thunk；
excludeChunks: 这个与chunks配置项正好相反，用来配置不允许注入的thunk。
chunksSortMode: none | auto| function，默认auto； 允许指定的thunk在插入到html文档前进行排序。
>function值可以指定具体排序规则；auto基于thunk的id进行排序； none就是不排序
xhtml: true|fasle, 默认false；是否渲染link为自闭合的标签，true则为自闭合标签
cache: true|fasle, 默认true； 如果为true表示在对应的thunk文件修改后就会emit文件
showErrors: true|false，默认true；是否将错误信息输出到html页面中。这个很有用，在生成html文件的过程中有错误信息，输出到页面就能看到错误相关信息便于调试。
minify: {....}|false；传递 html-minifier 选项给 minify 输出，false就是不使用html压缩。
下面的是一个用于配置这些属性的一个例子：
new HtmlWebpackPlugin({
title:'rd平台',
template: 'entries/index.html', // 源模板文件
filename: './index.html', // 输出文件【注意：这里的根路径是module.exports.output.path】
showErrors: true,
inject: 'body',
chunks: ["common",'index'] })配置多个html页面
html-webpack-plugin的一个实例生成一个html文件，如果单页应用中需要多个页面入口，或者多页应用时配置多个html时，那么就需要实例化该插件多次；
即有几个页面就需要在webpack的plugins数组中配置几个该插件实例：
...
plugins: [ new HtmlWebpackPlugin({
template: 'src/html/index.html',
excludeChunks: ['list', 'detail'] }),
new HtmlWebpackPlugin({
filename: 'list.html',
template: 'src/html/list.html',
thunks: ['common', 'list'] }),
new HtmlWebpackPlugin({
filename: 'detail.html',
template: 'src/html/detail.html',
thunks: ['common', 'detail'] })
]
...如上例应用中配置了三个入口页面：index.html、list.html、detail.html；并且每个页面注入的thunk不尽相同；类似如果多页面应用，就需要为每个页面配置一个；
配置自定义的模板
不带参数的html-webpack-plugin默认生成的html文件只是将thunk和css样式插入到文档中，可能不能满足我们的需求；
另外，如上面所述，三个页面指定了三个不同html模板文件；在项目中，可能所有页面的模板文件可以共用一个，因为html-webpack-plugin插件支持不同的模板loader，所以结合模板引擎来共用一个模板文件有了可能。
所以，配置自定义模板就派上用场了。具体的做法，借助于模板引擎来实现，例如插件没有配置loader时默认支持的ejs模板引擎，下面就以ejs模板引擎为例来说明；
例如项目中有2个入口html页面，它们可以共用一个模板文件，利用ejs模板的语法来动态插入各自页面的thunk和css样式，代码可以这样：
<!DOCTYPE html><html style="font-size:20px"><head>
<meta charset="utf-8">
<title><%= htmlWebpackPlugin.options.title %></title>
<% for (var css in htmlWebpackPlugin.files.css) { %>
<link href="<%=htmlWebpackPlugin.files.css[css] %>" rel="stylesheet">
<% } %></head><body><div id="app"></div>
<% for (var chunk in htmlWebpackPlugin.files.chunks) { %><script type="text/javascript" src=\'#\'" /script><% } %></body></html>你可能会对代码中的上下文htmlWebpackPlugin数据感到迷惑，这是啥东东？其实这是html-webpack-plugin插件在生成html文件过程中产生的数据，这些数据对html模板文件是可用的。
自定义模板上下文数据
html-webpack-plugin在生成html文件的过程中，插件会根据配置生成一个对当前模板可用的特定数据，模板语法可以根据这些数据来动态生成html文件的内容。
那么，插件生成的特殊数据格式是什么，生成的哪些数据呢？从源码或者其官网都给出了答案。从源码中可以看出模板引擎具体可以访问的数据如下:
var templateParams = {
compilation: compilation,
webpack: compilation.getStats().toJson(),
webpackConfig: compilation.options,
htmlWebpackPlugin:
files: assets,
options: self.options
}
};从中可以看出，有四个主要的对像数据。其中compilation为所有webpack插件提供的都可以访问的一个编译对象，此处就不太做介绍，具体可以自己查资料。下面就对剩下的三个对象数据进行说明。
webpack
webpack的stats对象；注意一点：
这个可以访问的stats对象是htm文件生成时所对应的stats对象，而不是webpack运行完成后所对应的整个stats对象。
webpackConfig
webpack的配置项；通过这个属性可以获取webpack的相关配置项，如通过webpackConfig.output.publicPath来获取publicPath配置。当然还可以获取其他配置内容。
htmlWebpackPlugin
html-webpack-plugin插件对应的数据。它包括两部分：
htmlWebpackPlugin.files: 此次html-webpack-plugin插件配置的chunk和抽取的css样式。该files值其实是webpack的stats对象的assetsByChunkName属性代表的值，该值是插件配置的chunk块对应的按照webpackConfig.output.filename映射的值。例如对应上面配置插件各个属性配置项例子中生成的数据格式如下：
"htmlWebpackPlugin": {
"files": {
"css": [ "inex.css" ],
"js": [ "common.js", "index.js"],
"chunks": {
"common": {
"entry": "common.js",
"css": [ "index.css" ] },
"index": {
"entry": "index.js",
"css": ["index.css"] }
}
}}这样，就可以是用如下模板引擎来动态输出script脚本
<% for (var chunk in htmlWebpackPlugin.files.chunks) { %><script type="text/javascript" src=\'#\'" /script><% } %>htmlWebpackPlugin.options: 传递给插件的配置项，具体的配置项如上面插件配置项小节所描述的。
插件事件
不知道你发现没有，html-webpack-plugin插件在插入静态资源时存在一些问题：
在插入js资源只能插入head或者body元素中，不能一些插入head中，另一些插入body中
不支持在html中文件内联*，例如在文件的某个地方用12fb87a978cd86bc393e6dfe44ecd2cc2cacc6d41bbb37262a98f745aa00fbf0来内联外部脚本
为此，有人专门给插件作者提问了这个问题；对此插件作者提供了插件事件，允许其他插件来改变html文件内容。具体的事件如下：
Async（异步事件）:
* html-webpack-plugin-before-html-generation
* html-webpack-plugin-before-html-processing
* html-webpack-plugin-alter-asset-tags
* html-webpack-plugin-after-html-processing
* html-webpack-plugin-after-emitSync（同步事件）:
* html-webpack-plugin-alter-chunks
这些事件是提供给其他插件使用的，用于改变html的内容。因此，要用这些事件需要提供一个webpack插件。例如下面定义的MyPlugin插件。
function MyPlugin(options) {
// Configure your plugin with options...}MyPlugin.prototype.apply = function(compiler) {
// ...
compiler.plugin('compilation', function(compilation) {
console.log('The compiler is starting a new compilation...');
compilation.plugin('html-webpack-plugin-before-html-processing', function(htmlPluginData, callback) {
htmlPluginData.html += 'The magic footer';
callback(null, htmlPluginData);
});
});};module.exports = MyPlugin;然后，在webpack.config.js文件中配置Myplugin信息：
plugins: [ new MyPlugin({options: ''})
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