Build process that transforms (multiple) SVG assets into a asset-parser compatible bundle
Last updated a year ago by swaagie .
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$ cnpm install asset-bundle 
SYNC missed versions from official npm registry.


Transforms your SVG assets in to asset-provider compatible bundle that contains multiple SVG assets.

The bundle process executes the following steps to produce a bundle:

  • read It reads out all the supplied paths that you supplied and generates the name of the asset based on the filename. If the root option is set, it will use the folder structure as "namespace", when the option is omitted the name of the asset is just file name without extension.
  • optimize The SVG's are optimized with svgo so all information that cannot be used is removed. This ensures that the assets that we bundle are as small as possible.
  • parse The optimized SVG structure is transformed to a DOM tree so we can start extracting and transforming.
  • viewBox In order to correctly render, and scale the assets we need to know the dimensions. We verify if a viewBox properly is available or we render the svg with puppeteer and extract the calculated SVG bounding box. The bounding box information is then used to construct the viewBox.
  • traverse We transform the SVG to an easy to parse format so minimal CPU needs to be used when transforming assets to svgs elements. We want to minimize impact to mobile device CPU's and battery life so this optimization step happens during the bundling phase.
  • encode The resulting transformed structure is then encoded using the asset-parser library.


npm install --save asset-bundle

The bundler has an optional dependency on puppeteer. This module is used to resolve the viewBox of a given svg asset if there is no viewBox or height/width combination available on the asset. If these properties are missing on some of your assets you can either manually update them, or install puppeteer and it will automatically extract the correct viewBox from your svg.

npm install --save puppeteer

Table of Contents


import Bundle from 'asset-bundle';

The Bundle constructor requires a single argument.

  • paths An array of paths that point to the SVG files that need to be included in the resulting bundle.
  • config Optional configuration that allows you to customize the SVGO process. Do not touch this unless you know what you're doing, like really know what you are doing.
import path from 'path';

const bundle = new Bundle([
  path.join(__dirname, 'folder', 'filename.svg'),
  path.join(__dirname, 'folder', 'another.svg'),
  path.join(__dirname, 'folder', 'more.svg')

The following config options are available:

  • root The root of the directory where the bundling process is taking place. This will be used to generate "namespaced" names of assets when they are deeply nested in folders.
  • multipass Enable or disable multipass in svgo. Defaults to false;
  • svgo An Array of plugins that need to be enabled in svgo. Highly recommended to not touch this, unless you know what you're doing, know the order of the svgo plugins, and which svgo plugins are vital for the conversion process.


Registers a new transformation hook that is ran on every element. This allows you to transform, remove or add addition attributes or even change the component completely.

The method requires 2 arguments:

  • name A unique name for your transformation
  • fn Function that does the actual transforming.
bundle.modify('what', function (attr, element, name) {


As you can see in the example above it receives 3 arguments in the transformation function:

  • attr An object that contains all attributes of the SVG elements.
  • element Reference to the DOM element of the SVG that we just parsed.
  • name Component name of the element.

If you want to modify the attributes you can just alter the attr object. If you wish to change the component name, you need to return a new name. We assume that you return undefined in all other cases as signal that the component name should not be changed.


Register a new plugin.

  • Plugin The constructor of the plugin function.
  • ...args The rest of the arguments for the plugin.
bundle.plugin(PluginConstructor, {
  options: 'for',
  the: 'plugin'

It returns the instance of the plugin for debugging sake.


Starts the transformation process of the supplied SVG files. Please note that this is a heavy operation and should really be done during build time of your assets.

The run method requires a single argument:

  • fn Error first completion callback. The first argument will be an optional error argument, the second argument will be the resulting bundle. The bundle is already encoded in the correct format that is accepted by the asset-parser library.
import path from 'path';
import fs from 'fs'; (err, str) {
  if (err) throw err; // Don't actually throw it, just handle it.

  fs.writeFileSync(path.join(__dirname, 'bundle.svgs'), str);

It is worth noting that we use the filename of each SVG as name for the asset. So when you're fetching this bundle using the asset-provider library your assets would be named:

  • filename
  • another
  • more

(As those were the files that our bundle example was using).


The Bundle extends EventEmitter and emits events during the various of transformation cycles. The following events are emitted (and in order):

  • read Supplied paths have been read.
  • optimize SVG's have been optimized.
  • parse AST has been generated from the SVGS.
  • viewBox All viewBox's have been calculated.
  • traverse AST has been traversed and output structure is generated.
  • done Structure has been encoded.

All events will receive the following arguments:

  • err An Error if that happens during the transformation step.
  • svgs An Array of SVG objects.

The only exception for this is the done event, which will receive:

  • err An Error if that happens during the transformation step.
  • result Encoded result.
  • svgs An Array of SVG objects.
bundle.on('done', (err, data, svgs) => {



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