eslint-plugin-html

A ESLint plugin to lint and fix inline scripts contained in HTML files.

Usage
Disabling ESLint
Linting HTML
Multiple scripts tags in a HTML file
- History
XML support
Settings
Troubleshooting
Migration from older versions
- To v4
- To v3
Credits

Usage

Simply install via npm install --save-dev eslint-plugin-html and add the plugin to your ESLint configuration. See ESLint documentation.

Example with ESLint 9 and above (flat config)

import html from "eslint-plugin-html"

export default [
  {
    files: ["**/*.html"],
    plugins: { html },
  },
]

Example with ESLint 8 and below

{
  "plugins": ["html"]
}

Disabling ESLint

To temporarily disable ESLint, use the  HTML comment. Re-enable it with . Example:

<!-- eslint-disable -->
<script>
  var foo = 1
</script>
<!-- eslint-enable -->

To disable ESLint for the next script tag only, use the  HTML comment. Example:

<!-- eslint-disable-next-script -->
<script>
  var foo = 1
</script>

Disabled script tags are completely ignored: their content will not be parsed as JavaScript. You can use this to disable script tags containing template syntax.

Linting HTML

This plugin focuses on applying ESLint rules on inline scripts contained in HTML. It does not provide any rule related to HTML. For that, you can use other plugins like @eslint-html or @angular-eslint. eslint-plugin-html is compatible with those plugins and can be used along them.

Multiple scripts tags in a HTML file

When linting a HTML with multiple script tags, this plugin tries to emulate the browser behavior by sharing the global scope between scripts by default. This behavior doesn't apply to "module" scripts (ie: <script type="module"> and most transpiled code), where each script tag gets its own top-level scope.

ESLint has already an option to tell the parser if the script are modules. eslint-plugin-html will use this option as well to know if the scopes should be shared (the default) or not. To change this, just set it in your ESLint configuration:

ESLint 9 and above (flat config)

export default [
  {
    // ...
    languageOptions: {
      sourceType: "module",
    },
  },
]

ESLint 8 and below

{
  "parserOptions": {
    "sourceType": "module"
  }
}

To illustrate this behavior, consider this HTML extract:

<script>
  var foo = 1
</script>

<script>
  alert(foo)
</script>

This is perfectly valid by default, and the ESLint rules no-unused-vars and no-undef shouldn't complain. But if those scripts are considerated as ES modules, no-unused-vars should report an error in the first script, and no-undef should report an error in the second script.

History

In eslint-plugin-html v1 and v2, script code were concatenated and linted in a single pass, so the scope were always shared. This caused some issues, so in v3 all scripts were linted separately, and scopes were never shared. In v4, the plugin still lint scripts separately, but makes sure global variables are declared and used correctly in the non-module case.

XML support

This plugin parses HTML and XML markup slightly differently, mainly when considering CDATA sections:

in XML, any data inside a CDATA section will be considered as raw text (not XML) and the CDATA delimiter will be droped ;
in HTML, there is no such thing for <script> tags: the CDATA delimiter is considered as normal text and thus, part of the script.

Settings

Note: all settings can be written either as "html/key": value or in a nested object "html": { "key": value }

`html/html-extensions`

By default, this plugin will only consider files ending with those extensions as HTML: .erb, .handlebars, .hbs, .htm, .html, .mustache, .nunjucks, .php, .tag, .twig, .we. You can set your own list of HTML extensions by using this setting. Example:

ESLint 9 and above (flat config)

export default [
  {
    files: ["**/*.html", "**/*.we"],
    plugins: { html },
    settings: {
      "html/html-extensions": [".html", ".we"], // consider .html and .we files as HTML
    },
  },
]

Note: you need to specify extensions twice, which is not ideal. This should be imporved in the future.

ESLint 8 and below

{
  "plugins": ["html"],
  "settings": {
    "html/html-extensions": [".html", ".we"] // consider .html and .we files as HTML
  }
}

`html/xml-extensions`

By default, this plugin will only consider files ending with those extensions as XML: .xhtml, .xml. You can set your own list of XML extensions by using this setting. Example:

ESLint 9 and above (flat config)

export default [
  {
    files: ["**/*.html"],
    plugins: { html },
    settings: {
      "html/xtml-extensions": [".html"], // consider .html files as XML
    },
  },
]

Note: you need to specify extensions twice, which is not ideal. This should be imporved in the future.

ESLint 8 and below

{
  "plugins": ["html"],
  "settings": {
    "html/xml-extensions": [".html"] // consider .html files as XML
  }
}

`html/indent`

By default, the code between <script> tags is dedented according to the first non-empty line. The setting html/indent allows to ensure that every script tags follow an uniform indentation. Like the indent rule, you can pass a number of spaces, or "tab" to indent with one tab. Prefix this value with a + to be relative to the <script> tag indentation. Example:

ESLint 9 and above (flat config)

export default [
  {
    files: ["**/*.html"],
    plugins: { html },
    settings: {
      "html/indent": "0", // code should start at the beginning of the line (no initial indentation).
      "html/indent": "+2", // indentation is the <script> indentation plus two spaces.
      "html/indent": "tab", // indentation is one tab at the beginning of the line.
    },
  },
]

ESLint 8 and below

{
  "plugins": ["html"],
  "settings": {
    "html/indent": "0", // code should start at the beginning of the line (no initial indentation).
    "html/indent": "+2", // indentation is the <script> indentation plus two spaces.
    "html/indent": "tab" // indentation is one tab at the beginning of the line.
  }
}

`html/report-bad-indent`

By default, this plugin won't warn if it encounters a problematic indentation (ex: a line is under indented). If you want to make sure the indentation is correct, use the html/report-bad-indent in conjunction with the indent rule. Pass "warn" or 1 to display warnings, "error" or 2 to display errors. Example:

ESLint 9 and above (flat config)

export default [
  {
    files: ["**/*.html"],
    plugins: { html },
    settings: {
      "html/report-bad-indent": "error",
    },
  },
]

ESLint 8 and below

{
  "plugins": ["html"],
  "settings": {
    "html/report-bad-indent": "error"
  }
}

`html/javascript-tag-names`

By default, the code between <script> tags is considered as JavaScript. You can customize which tags should be considered JavaScript by providing one or multiple tag names.

Example:

ESLint 9 and above (flat config)

export default [
  {
    files: ["**/*.html"],
    plugins: { html },
    settings: {
      "html/javascript-tag-names": ["script", "customscript"],
    },
  },
]

ESLint 8 and below

{
  "plugins": ["html"],
  "settings": {
    "html/javascript-tag-names": ["script", "customscript"]
  }
}

`html/javascript-mime-types`

By default, the code between <script> tags is considered as JavaScript code only if there is no type attribute or if its value matches the pattern (application|text)/(x-)?(javascript|babel|ecmascript-6) or module (case insensitive). You can customize the types that should be considered as JavaScript by providing one or multiple MIME types. If a MIME type starts with a /, it will be considered as a regular expression. Example:

ESLint 9 and above (flat config)

export default [
  {
    files: ["**/*.html"],
    plugins: { html },
    settings: {
      "html/javascript-mime-types": ["text/javascript", "text/jsx"], // also use script tags with a "text/jsx" type attribute
      "html/javascript-mime-types": "/^text\\/(javascript|jsx)$/", // same thing
    },
  },
]

ESLint 8 and below

{
  "plugins": ["html"],
  "settings": {
    "html/javascript-mime-types": ["text/javascript", "text/jsx"], // also use script tags with a "text/jsx" type attribute
    "html/javascript-mime-types": "/^text\\/(javascript|jsx)$/" // same thing
  }
}

`html/ignore-tags-without-type`

By default, the code between <script> tags is considered JavaScript if there is no type attribute. You can set this setting to true to ignore script tags without a type attribute. Example:

ESLint 9 and above (flat config)

export default [
  {
    files: ["**/*.html"],
    plugins: { html },
    settings: {
      "html/ignore-tags-without-type": true,
    },
  },
]

ESLint 8 and below

{
  "plugins": ["html"],
  "settings": {
    "html/ignore-tags-without-type": true
  }
}

Troubleshooting

No file linted when running `eslint` on a directory

By default, when executing the eslint command on a directory, only .js files will be linted. You will have to specify extra extensions with the --ext option. Example: eslint --ext .html,.js src will lint both .html and .js files in the src directory. See ESLint documentation.

Linting templates (or PHP)

eslint-plugin-html won't evaluate or remove your template markup. If you have template markup in your script tags, the resulting script may not be valid JavaScript, so ESLint will fail to parse it. Here are some workarounds:

You can use HTML comments to disable ESLint for specific script tags.
For PHP, you can use eslint-plugin-php-markup to lint php files, it use a same way to process php markup like eslint-plugin-html.
Another possible hacky workaround to make sure the code is valid JavaScript is to put your template markup inside a comment. When the template is rendered, the generated JS code must start with a new line, so it will be written below the comment. PHP example:

<script>
  var mydata
  // <?= "\n mydata = " . json_encode($var) . ";" ?>
  console.log(mydata)
</script>

Linting VUE files

Initially, eslint-plugin-vue was using eslint-plugin-html to lint code inside script tags. Since v3, eslint-plugin-vue is using its own parser, so it is incompatible with eslint-plugin-html. You should use eslint-plugin-vue exclusively and remove eslint-plugin-html from your dependencies if you still have it.

Migration from older versions

To v4

eslint-plugin-html v4 requires at least ESLint v4.7. This is because a lot of internal changes occured in ESLint v4.7, including a new API to support autofixing in preprocessors. If you are still using an older version of ESLint, please consider upgrading, or keep using eslint-plugin-html v3.

The big feature (and breaking change) in eslint-plugin-html v4 is the ability to choose how scopes are shared between script tags in the same HTML file.

To v3

If you are considering upgrading to v3, please read this guide.

Credits

A big thank you to @kuceb for the logo image!