minify-html-literals

Minify HTML markup inside JavaScript template literal strings.

Why?

Template literals are often used in JavaScript to write HTML and CSS markup (ex. lit-html). This library allows a developer to minify markup that is normally ignored by JavaScript minifiers.

Usage

import { minifyHTMLLiterals } from 'minify-html-literals';
// const minifyHTMLLiterals = require('minify-html-literals').minifyHTMLLiterals

const result = minifyHTMLLiterals(
  `function render(title, items) {
    return html\`
      <style>
        .heading {
          color: blue;
        }
      </style>
      <h1 class="heading">\${title}</h1>
      <ul>
        \${items.map(item => {
          return getHTML()\`
            <li>\${item}</li>
          \`;
        })}
      </ul>
    \`;
  }`,
  {
    fileName: 'render.js'
  }
);

console.log(result.code);
//  function render(title, items) {
//    return html`<style>.heading{color:#00f}</style><h1 class=heading>${title}</h1><ul>${items.map(item => {
//          return getHTML()`<li>${item}</li>`;
//        })}</ul>`;
//  }

console.log(result.map);
// {
//   "version": 3,
//   "file": "render.js.map",
//   "sources": ["render.js"],
//   "sourcesContent": [null],
//   "names": [],
//   "mappings": "AAAA;gBACgB,qDAMU,QAAQ,SAE1B;2BACmB,IACX,OAAO,KACb;WACC,KAEP;"
// }

ES5 Transpiling Warning

Be sure to minify template literals before transpiling to ES5. Otherwise, the API will not be able to find any template literal (`${}`) strings.

Supported Source Syntax

• JavaScript
• TypeScript

Options

Basic

The following options are common to typical use cases.

Advanced

All aspects of the API are exposed and customizable. The following options will not typically be used unless you need to change how a certain aspect of the API handles a use case.

Customization Examples

Minify non-tagged templates

This is particularly useful for libraries that define templates without using tags, such as Polymer's <dom-module>.

import { minifyHTMLLiterals, defaultShouldMinify } from 'minify-html-literals';

minifyHTMLLiterals(
  `
    template.innerHTML = \`
      <dom-module id="custom-styles">
        <style>
          html {
            --custom-color: blue;
          }
        </style>
      </dom-module>
    \`;
  `,
  {
    fileName: 'render.js',
    shouldMinify(template) {
      return (
        defaultShouldMinify(template) ||
        template.parts.some(part => {
          return part.text.includes('<dom-module>');
        })
      );
    }
  }
);

Do not minify CSS

import { minifyHTMLLiterals, defaultMinifyOptions } from 'minify-html-literals';

minifyHTMLLiterals(source, {
  fileName: 'render.js',
  minifyOptions: {
    ...defaultMinifyOptions,
    minifyCSS: false
  },
  shouldMinifyCSS: () => false
});

Modify generated SourceMap

minifyHTMLLiterals(source, {
  fileName: 'render.js',
  generateSourceMap(ms, fileName) {
    return ms.generateMap({
      file: `${fileName}-converted.map`, // change file name
      source: fileName,
      includeContent: true // include source contents
    });
  }
});