Svelte CLI

Build Targets

When you run vue-cli-service build, you can specify different build targets via the --target option. This allows you to use the same code base to produce different builds for different use cases.

App

App is the default build target. In this mode:

  • index.html with asset and resource hints injection
  • vendor libraries split into a separate chunk for better caching
  • static assets under 4kb are inlined into JavaScript
  • static assets in public are copied into output directory

Library

Note on Vue Dependency

In lib mode, Vue is externalized. This means the bundle will not bundle Vue even if your code imports Vue. If the lib is used via a bundler, it will attempt to load Vue as a dependency through the bundler; otherwise, it falls back to a global Vue variable.

You can build a single entry as a library using

vue-cli-service build --target lib --name myLib [entry]

File                     Size                     Gzipped

dist/myLib.umd.min.js    13.28 kb                 8.42 kb
dist/myLib.umd.js        20.95 kb                 10.22 kb
dist/myLib.common.js     20.57 kb                 10.09 kb
dist/myLib.css           0.33 kb                  0.23 kb

The entry can be either a .js or a .vue file. If no entry is specified, src/App.vue will be used.

A lib build outputs:

  • dist/myLib.common.js: A CommonJS bundle for consuming via bundlers (unfortunately, webpack currently does not support ES modules output format for bundles yet)

  • dist/myLib.umd.js: A UMD bundle for consuming directly in browsers or with AMD loaders

  • dist/myLib.umd.min.js: Minified version of the UMD build.

  • dist/myLib.css: Extracted CSS file (can be forced into inlined by setting css: { extract: false } in svelte.config.js)

Vue vs. JS/TS Entry Files

When using a .vue file as entry, your library will directly expose the Vue component itself, because the component is always the default export.

However, when you are using a .js or .ts file as your entry, it may contain named exports, so your library will be exposed as a Module. This means the default export of your library must be accessed as window.yourLib.default in UMD builds, or as const myLib = require('mylib').default in CommonJS builds. If you don't have any named exports and wish to directly expose the default export, you can use the following webpack configuration in svelte.config.js:

module.exports = {
  configureWebpack: {
    output: {
      libraryExport: 'default'
    }
  }
}

Web Component

Note on Compatibility

Web Component mode does not support IE11 and below. More details

Note on Vue Dependency

In web component mode, Vue is externalized. This means the bundle will not bundle Vue even if your code imports Vue. The bundle will assume Vue is available on the host page as a global variable.

You can build a single entry as a web component using

vue-cli-service build --target wc --name my-element [entry]

Note that the entry should be a *.vue file. Vue CLI will automatically wrap and register the component as a Web Component for you, and there's no need to do this yourself in main.js. You can use main.js as a demo app solely for development.

The build will produce a single JavaScript file (and its minified version) with everything inlined. The script, when included on a page, registers the <my-element> custom element, which wraps the target Vue component using @vue/web-component-wrapper. The wrapper automatically proxies properties, attributes, events and slots. See the docs for @vue/web-component-wrapper for more details.

Note the bundle relies on Vue being globally available on the page.

This mode allows consumers of your component to use the Vue component as a normal DOM element:

<script src="https://unpkg.com/vue"></script>
<script src="path/to/my-element.js"></script>

<!-- use in plain HTML, or in any other framework -->
<my-element></my-element>

Bundle that Registers Multiple Web Components

When building a web component bundle, you can also target multiple components by using a glob as entry:

vue-cli-service build --target wc --name foo 'src/components/*.vue'

When building multiple web components, --name will be used as the prefix and the custom element name will be inferred from the component filename. For example, with --name foo and a component named HelloWorld.vue, the resulting custom element will be registered as <foo-hello-world>.

Async Web Component

When targeting multiple web components, the bundle may become quite large, and the user may only use a few of the components your bundle registers. The async web component mode produces a code-split bundle with a small entry file that provides the shared runtime between all the components, and registers all the custom elements upfront. The actual implementation of a component is then fetched on-demand only when an instance of the corresponding custom element is used on the page:

vue-cli-service build --target wc-async --name foo 'src/components/*.vue'

File                Size                        Gzipped

dist/foo.0.min.js    12.80 kb                    8.09 kb
dist/foo.min.js      7.45 kb                     3.17 kb
dist/foo.1.min.js    2.91 kb                     1.02 kb
dist/foo.js          22.51 kb                    6.67 kb
dist/foo.0.js        17.27 kb                    8.83 kb
dist/foo.1.js        5.24 kb                     1.64 kb

Now on the page, the user only needs to include Vue and the entry file:

<script src="https://unpkg.com/vue"></script>
<script src="path/to/foo.min.js"></script>

<!-- foo-one's implementation chunk is auto fetched when it's used -->
<foo-one></foo-one>

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