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
  • html/html-extensions
  • html/xml-extensions
  • html/indent
  • html/report-bad-indent
  • html/javascript-tag-names
  • html/javascript-mime-types
  • html/ignore-tags-without-type
• Troubleshooting
  • No file linted when running eslint on a directory
  • Linting templates (or PHP)
  • Linting VUE files
• 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:

 {
    "plugins": [
        "html"
    ]
}

Disabling ESLint

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

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

To disable ESLint for the next script tag only, use the <!-- eslint-disable-next-script --> 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:

{
  "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:

 {
    "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:

 {
    "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:

 {
    "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:

 {
    "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:

 {
    "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:

 {
    "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:

 {
    "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!