file-loader

file-loader

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The file-loader resolves import/require() on a file into a url and emits the file into the output directory.

起步

你需要预先安装 file-loader：

$ npm install file-loader --save-dev

在一个 bundle 文件中 import（或 require）目标文件：

file.js

import img from './file.png';

然后，在 webpack 配置中添加 loader。例如：

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {},
          },
        ],
      },
    ],
  },
};

然后，通过你偏爱的方式去运行 webpack。将 file.png 作为一个文件，生成到输出目录，（如果指定了选项，则使用指定的命名约定）并返回文件的 public URI。

ℹ️ 默认情况下，生成文件的文件名，是文件内容的 MD5 哈希值，并会保留所引用资源的原始扩展名。

选项

`name`

类型：String|Function 默认：'[hash].[ext]'

Specifies a custom filename template for the target file(s) using the query parameter name. For example, to emit a file from your context directory into the output directory retaining the full directory structure, you might use:

`String`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[path][name].[ext]',
            },
          },
        ],
      },
    ],
  },
};

`Function`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name(file) {
                if (process.env.NODE_ENV === 'development') {
                  return '[path][name].[ext]';
                }
                return '[hash].[ext]';
              },
            },
          },
        ],
      },
    ],
  },
};

ℹ️ 默认情况下，文件会按照你指定的路径和名称输出同一目录中，且会使用相同的 URI 路径来访问文件。

`outputPath`

类型：String|Function 默认：undefined

Specify a filesystem path where the target file(s) will be placed.

`String`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              outputPath: 'images',
            },
          },
        ],
      },
    ],
  },
};

`Function`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              outputPath: (url, resourcePath, context) => {
                // `resourcePath` is original absolute path to asset
                // `context` is directory where stored asset (`rootContext`) or `context` option
                // To get relative path you can use
                // const relativePath = path.relative(context, resourcePath);
                if (/my-custom-image\.png/.test(resourcePath)) {
                  return `other_output_path/${url}`;
                }
                if (/images/.test(context)) {
                  return `image_output_path/${url}`;
                }
                return `output_path/${url}`;
              },
            },
          },
        ],
      },
    ],
  },
};

`publicPath`

类型：String|Function 默认：__webpack_public_path__

Specifies a custom public path for the target file(s).

`String`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              publicPath: 'assets',
            },
          },
        ],
      },
    ],
  },
};

`Function`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              publicPath: (url, resourcePath, context) => {
                // `resourcePath` is original absolute path to asset
                // `context` is directory where stored asset (`rootContext`) or `context` option
                // To get relative path you can use
                // const relativePath = path.relative(context, resourcePath);
                if (/my-custom-image\.png/.test(resourcePath)) {
                  return `other_public_path/${url}`;
                }
                if (/images/.test(context)) {
                  return `image_output_path/${url}`;
                }
                return `public_path/${url}`;
              },
            },
          },
        ],
      },
    ],
  },
};

`context`

类型：String 默认：context

Specifies a custom file context.

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              context: 'project',
            },
          },
        ],
      },
    ],
  },
};

`emitFile`

类型：Boolean 默认：true

如果是 true，生成一个文件（向文件系统写入一个文件）。如果是 false，loader 会返回 public URI，但不会生成文件。对于服务器端 package，禁用此选项通常很有用。

file.js

// bundle file
import img from './file.png';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              emitFile: false,
            },
          },
        ],
      },
    ],
  },
};

`regExp`

类型：RegExp 默认：undefined

Specifies a Regular Expression to one or many parts of the target file path. The capture groups can be reused in the name property using [N] placeholder.

file.js

import img from './customer01/file.png';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              regExp: /\/([a-z0-9]+)\/[a-z0-9]+\.png$/,
              name: '[1]-[name].[ext]',
            },
          },
        ],
      },
    ],
  },
};

ℹ️ If [0] is used, it will be replaced by the entire tested string, whereas [1] will contain the first capturing parenthesis of your regex and so on…

placeholders

Full information about placeholders you can find here.

`[ext]`

类型：String 默认：file.extname

目标文件/资源的文件扩展名。

`[name]`

类型：String 默认：file.basename

文件/资源的基本名称。

`[path]`

类型：String 默认：file.directory

The path of the resource relative to the webpack/config context.

`[folder]`

类型：String 默认：file.folder

The folder of the resource is in.

`[emoji]`

类型：String 默认：undefined

A random emoji representation of content.

`[emoji:<length>]`

类型：String 默认：undefined

Same as above, but with a customizable number of emojis

`[hash]`

类型：String 默认：md5

指定生成文件内容哈希值的哈希方法。

`[<hashType>:hash:<digestType>:<length>]`

类型：String

The hash of options.content (Buffer) (by default it’s the hex digest of the hash).

`digestType`

类型：String 默认：'hex'

The digest that the hash function should use. Valid values include: base26, base32, base36, base49, base52, base58, base62, base64, and hex.

`hashType`

类型：String 默认：'md5'

The type of hash that the has function should use. Valid values include: md5, sha1, sha256, and sha512.

`length`

类型：Number 默认：undefined

Users may also specify a length for the computed hash.

`[N]`

类型：String 默认：undefined

The n-th match obtained from matching the current file name against the regExp.

示例

The following examples show how one might use file-loader and what the result would be.

file.js

import png from './image.png';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: 'dirname/[hash].[ext]',
            },
          }
        ],
      },
    ],
  },
};

结果：

# result
dirname/0dcbbaa701328ae351f.png

file.js

import png from './image.png';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[sha512:hash:base64:7].[ext]',
            },
          },
        ],
      },
    ],
  },
};

结果：

# result
gdyb21L.png

file.js

import png from './path/to/file.png';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[path][name].[ext]?[hash]',
            },
          },
        ],
      },
    ],
  },
};

结果：

# result
path/to/file.png?e43b20c069c4a01867c31e98cbce33c9

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License

MIT