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svelte-assets-preprocessor

A Svelte preprocessor that extracts assets.

Overview

This preprocessor is based on the webpack html-loader. It works in a similar way and shares some config options.

Installation

Using npm:

$ npm i -D svelte-assets-preprocessor

Example

Input

<img src="./example.png">

Output

<script>
    import ___ASSET___1 from './example.png';
</script>

<img src="{___ASSET___1}">

Usage

With rollup-plugin-svelte

You will need to use @rollup/plugin-url to load assets.

// rollup.config.js
import svelte from 'rollup-plugin-svelte';
import assetsPreprocessor from 'svelte-assets-preprocessor'
import url from '@rollup/plugin-url'

export default {
  ...,
  plugins: [
    url({ destDir: 'public' }),
    svelte({
      preprocess: assetsPreprocessor({ /* options */ })
    })
  ]
}

With svelte-loader

You will need to install another loader to handle the imports appropriately such as file-loader or url-loader.

  ...
  module: {
    rules: [
      ...
      {
        test: /\.(png|svg|jpg|gif)$/,
        loader: 'file-loader',
        options: {
          outputPath: 'images',
        }
      },
      {
        test: /\.(html|svelte)$/,
        exclude: /node_modules/,
        use: {
          loader: 'svelte-loader',
          options: {
            preprocess: require('svelte-assets-preprocessor')({ /* options */ exclude: [ (attr) => !/\.(png|svg|jpg|gif)$/.test(attr)} ])
          },
        },
      },
      ...
    ]
  }
  ...

With Sapper

Sapper has two build configurations, one for the client bundle and one for the server. To use svelte-assets-preprocessor with Sapper, you need to define it on both configurations. You will need to use @rollup/plugin-url to load assets.

// ...
import assetsPreprocessor from 'svelte-assets-preprocessor';
import path from 'path';
import url from '@rollup/plugin-url';

const preprocess = assetsPreprocessor({});

export default {
  client: {
    plugins: [
      svelte({
        preprocess,
        // ...
      }),
      url({
        fileName: path.join('client', 'assets', '[name].[hash][extname]'),
        destDir: path.resolve(config.client.output().dir, '..')
      }),
  },
  server: {
    plugins: [
      svelte({
        preprocess,
        // ...
      }),
      url({
        fileName: path.join('server', 'assets', '[name].[hash][extname]'),
        destDir: path.resolve(config.server.output().dir, '..')
      }),
    ],
  },
};

With SvelteKit

With Sveltekit, svelte-preprocess is not a requirement if you just need to preprocess assets.

You can also configure your assets folder using kit.files.assets.

// svelte.config.js
import assetsPreprocessor from 'svelte-assets-preprocessor';

const config = {
    preprocess: [assetsPreprocessor()],
    kit: {
        files: {
		assets: 'static'
        }
        // ...
    }
    // ...
};

Options

attributes

A list of tags and attributes to process. For each tag and attribute a type is provided ('src' or 'srcset') and an optional filter function. The filter function can be used to add further conditions.

Default

[
  {
    tag: 'audio',
    attribute: 'src',
    type: 'src',
  },
  {
    tag: 'embed',
    attribute: 'src',
    type: 'src',
  },
  {
    tag: 'img',
    attribute: 'src',
    type: 'src',
  },
  {
    tag: 'img',
    attribute: 'srcset',
    type: 'srcset',
  },
  {
    tag: 'input',
    attribute: 'src',
    type: 'src',
  },
  {
    tag: 'link',
    attribute: 'href',
    type: 'src',
    filter: (tag, attribute, attributes) => {
      if (!attributes.rel || !/stylesheet/i.test(attributes.rel)) {
        return false;
      }

      if (
        attributes.type &&
        attributes.type.trim().toLowerCase() !== 'text/css'
      ) {
        return false;
      }

      return true;
    },
  },
  {
    tag: 'object',
    attribute: 'data',
    type: 'src',
  },
  {
    tag: 'script',
    attribute: 'src',
    type: 'src',
  },
  {
    tag: 'source',
    attribute: 'src',
    type: 'src',
  },
  {
    tag: 'source',
    attribute: 'srcset',
    type: 'srcset',
  },
  {
    tag: 'track',
    attribute: 'src',
    type: 'src',
  },
  {
    tag: 'video',
    attribute: 'poster',
    type: 'src',
  },
  {
    tag: 'video',
    attribute: 'src',
    type: 'src',
  },
];

exclude

A list of functions used to exclude specific assets.

Default []

Example

Only apply to images with specific extensions.

...
exclude: [ (attr) => !/\.(png|svg|jpg|gif)$/.test(attr)} ]
...

http

Process urls starting with http. This is disabled by default.

Default false

prefix

The prefix used for generated variable names.

Default ___ASSET___