What changed in style-loader from 3 to 4

4.0.0 (2024-04-08)

⚠ BREAKING CHANGES

• minimum supported webpack version is 5.27.0
• minimum support Node.js version is 18.12.0
• the insert option can only be a selector or the path to the module

Migration:

Before:

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [
          {
            loader: "style-loader",
            options: {
              injectType: "styleTag",
              styleTagTransform: function (css, style) {
                // Do something ...
                style.innerHTML = `${css}.modify{}\n`;

                document.head.appendChild(style);
              },
            },
          },
          "css-loader",
        ],
      },
    ],
  },
};

After:

insert-function.js

function insert(css, style) {
  var parent = options.target || document.head;

  parent.appendChild(element);
}

module.exports = insert;

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [
          {
            loader: "style-loader",
            options: {
              insert: require.resolve("./insert.js"),
            },
          },
          "css-loader",
        ],
      },
    ],
  },
};

• the styleTagTransform option can only be the path to the module

Migration:

Before:

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [
          {
            loader: "style-loader",
            options: {
              injectType: "styleTag",
              styleTagTransform: function (css, style) {
                // Do something ...
                style.innerHTML = `${css}.modify{}\n`;

                document.head.appendChild(style);
              },
            },
          },
          "css-loader",
        ],
      },
    ],
  },
};

After:

style-tag-transform-function.js

function styleTagTransform(css, style) {
  // Do something ...
  style.innerHTML = `${css}.modify{}\n`;

  document.head.appendChild(style);
}

module.exports = styleTagTransform;

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [
          {
            loader: "style-loader",
            options: {
              styleTagTransform: require.resolve("./style-tag-transform-function.js"),
            },
          },
          "css-loader",
        ],
      },
    ],
  },
};

Bug Fixes

• css experiments logic (#617) (8b9fc97)