html.tags
- Type:
ArrayOrNot<HtmlTag | HtmlTagHandler>
- Default:
undefined
Modifies the tags that are injected into the HTML page.
Tag Object
type HtmlTag = {
tag: string;
attrs?: Record<string, string | boolean | null | undefined>;
children?: string;
/** @default false */
hash?: boolean | string | ((url: string, hash: string) => string);
/** @default true */
publicPath?: boolean | string | ((url: string, publicPath: string) => string);
/**
* Sets the insertion position of the current tag relative to the original tags.
* If set to `true` it will be inserted after the original tags, if set to `false` it will be inserted before the original tags.
* @default true
*/
append?: boolean;
/**
* Whether to add tags to head
* Enable by default only for elements that are allowed to be included in the `head` tag.
* @see {@link https://developer.mozilla.org/en-US/docs/Web/HTML/Element/head#see_also}
*/
head?: boolean;
};
A tag object can be used to describe the tag to be injected and the location of the injection can be controlled by the parameters.
export default {
output: {
assetPrefix: 'https://example.com/',
},
html: {
tags: [
{
tag: 'script',
attrs: { src: 'a.js' },
head: true,
append: true,
publicPath: true,
hash: true,
},
],
},
};
It will add a script tag to the end of the head of the HTML:
<html>
<head>
<!-- some other headTags... -->
<script src="https://example.com/a.js?8327ec63"></script>
</head>
<body>
<!-- some other bodyTags... -->
</body>
</html>
Fields in the tag that indicate the path to the external assets are affected by the publicPath and hash options.
These fields include src for the script tag and href for the link tag.
Enabling publicPath will splice the output.assetPrefix field before the attribute representing the path in the tag.
And the hash field causes the filename to be followed by an additional hash query to control browser caching, with the same hash string as the HTML file product.
You can also pass functions to those fields to control the path joining.
Set tag insertion position
The final insertion position of the tag is determined by the head and append options, and two elements with the same configuration will be inserted into the same area and hold their relative positions to each other.
append: used to describe whether the tag is added to the end or beginning of the original tagshead: used to describe whether to add this tag to the HTML <head>
The final insertion position on the page is as follows:
<html>
<head>
<!-- tags with `{ head: true, append: false }` here. -->
<!-- some other headTags... -->
<!-- tags with `{ head: true, append: true }` here. -->
</head>
<body>
<!-- tags with `{ head: false, append: false }` here. -->
<!-- some other bodyTags... -->
<!-- tags with `{ head: false, append: true }` here. -->
</body>
</html>
Tags Handler
type HtmlTagUtils = {
hash: string;
entryName: string;
outputName: string;
publicPath: string;
};
type HtmlTagHandler = (
tags: HtmlTag[],
utils: HtmlTagUtils,
) => HtmlTag[] | void;
html.tags can also accept functions that can arbitrarily modify tags by writing logic to the callback, often used to ensure the relative position of tags while inserting them.
The callback function accepts a tag list as an argument and needs to modify or return a new tag array directly.
export default {
html: {
tags: [
(tags) => [{ tag: 'script', attrs: { src: 'a.js' } }, ...tags],
(tags) => {
// Modify 'a.js' tag
const target = tags.find((tag) => tag.attrs?.src === 'a.js');
if (target) {
target.attrs!.defer = true;
}
},
(tags) => {
// Insert 'b.js' after 'a.js'
const targetIndex = tags.findIndex((tag) => tag.attrs?.src === 'a.js');
tags.splice(targetIndex + 1, 0, {
tag: 'script',
attrs: { src: 'd.js' },
});
},
],
},
};
The HTML file will look like:
<html>
<head>
<script src="/a.js" defer></script>
<script src="/d.js"></script>
<!-- some other headTags... -->
</head>
<body>
<!-- some bodyTags... -->
</body>
</html>
Limitation
This configuration is used to modify the content of HTML files after Rsbuild completes building, and does not resolve or parse new modules. It cannot be used to import un-compiled source code files. Also cannot replace configurations such as source.preEntry.
For example, for the following project:
web-app
├── src
│ ├── index.tsx
│ └── polyfill.ts
└── rsbuild.config.ts
rsbuild.config.ts
export default {
output: {
assetPrefix: 'https://example.com/',
},
html: {
tags: [{ tag: 'script', attrs: { src: './src/polyfill.ts' } }],
},
};
The tag object here will be directly added to the HTML product after simple processing, but the polyfill.ts will not be transpiled or bundled, so there will be a 404 error when processing this script in the application.
<body>
<script src="https://example.com/src/polyfill.ts"></script>
</body>
Reasonable use cases include:
- Injecting static assets with determined paths on CDN.
- Injecting inline scripts that need to be loaded on the first screen.
For example, the usage of the following example:
web-app
├── src
│ └── index.tsx
├── public
│ └── service-worker.js
└── rsbuild.config.ts
rsbuild.config.ts
function report() {
fetch('https://www.example.com/report');
}
export default {
html: {
output: {
assetPrefix: 'https://example.com/',
},
tags: [
// Inject asset from the `public` directory.
{ tag: 'script', attrs: { src: 'service-worker.js' } },
// Inject asset from other CDN url.
{
tag: 'script',
publicPath: false,
attrs: { src: 'https://cdn.example.com/foo.js' },
},
// Inject inline script.
{
tag: 'script',
children: report.toString() + '\nreport()',
},
],
},
};
The result will seems like:
<body>
<script src="https://example.com/service-worker.js"></script>
<script src="https://cdn.example.com/foo.js"></script>
<script>
function report() {
fetch('https://www.example.com/report');
}
report();
</script>
</body>
