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0f22337 Mar 21, 2017
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@JeffreyWay @kohenkatz
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Library Code Splitting

mix.js(src, output)
   .extract(['any', 'vendor', 'library']);

Bundling all JavaScript into a single files does come with a potential downside: each time you change a minor detail in your application code, you must bust the cache for all users. That means all of your vendor libraries must be re-downloaded and cached. Yikes - not ideal!

One solution is to isolate, or extract, your vendor libraries into their own file.

  • Application Code: app.js
  • Vendor Libraries: vendor.js
  • Manifest (webpack Runtime): manifest.js
mix.extract(['vue', 'jquery']);

The extract method expects an array of vendor libraries that you wish to extract from your main bundle file. With this adjustment, the source code for both Vue and jQuery will be located in vendor.js, rather than app.js. Should you, in the future, need to make a small change to your application JavaScript, it will not affect the larger vendor libraries. Those will remain cached, long-term. Nifty!

Once you run webpack to compile your code, you'll find three new files. You may reference these at the bottom of your HTML, per usual.

<script src="/js/manifest.js"></script>
<script src="/js/vendor.js"></script>
<script src="/js/app.js"></script>

In effect, we pay a small HTTP request penalty, in exchange for improved long-term caching.

What's That Manifest File?

webpack compiles with a small bit of run-time code, to assist with its job. When not using mix.extract(), this code is invisible to you, and lives inside your bundle file. However, if we want to split our code and allow for long-term caching, that runtime code needs to live somewhere. As such, mix will extract it to its own file as well. This way, both your vendor and manifest files can be cached as long as possible.