factor browser-pack bundles into a common bundle and entry-specific bundles

x.js:

var z = require('./z.js');
var w = require('./w.js');
console.log(z(5) * w(2));

y.js:

var z = require('./z.js');
console.log(z(2) + 111);

z.js:

module.exports = function (n) { return n * 111 }

w.js:

module.exports = function (n) { return n * 50 }

Now run factor-bundle as a plugin (new in browserify 3.28.0):

browserify x.js y.js -p [ factor-bundle -o bundle/x.js -o bundle/y.js ] \
  -o bundle/common.js

or you can pipe module-deps json directly into the factor-bundle command:

$ module-deps x.js y.js | factor-bundle \
  x.js -o bundle/x.js \
  y.js -o bundle/y.js \
  > bundle/common.js

or factor out an existing bundle already compiled by browserify:

$ browserify x.js y.js > bundle.js
$ browser-unpack < bundle.js | factor-bundle \
  x.js -o bundle/x.js \
  y.js -o bundle/y.js \
  > bundle/common.js

Whichever one of these 3 options, you take, you can now have 2 pages, each with a different combination of script tags but with all the common modules factored out into a common.js to avoid transferring the same code multiple times:

<script src="/bundle/common.js"></script>
<script src="/bundle/x.js"></script>

<script src="/bundle/common.js"></script>
<script src="/bundle/y.js"></script>

to verify this works from node you can do:

$ cat bundle/common.js bundle/x.js | node
55500
$ cat bundle/common.js bundle/y.js | node
333

You can use factor-bundle as a browserify plugin:

browserify -p [ factor-bundle OPTIONS ]

where OPTIONS are:

  -o  Output file that maps to a corresponding entry file at the same index
 
  -e  Entry file to use, overriding the entry files listed in the original
      bundle.

or you can use the command:

usage: factor-bundle [ x.js -o bundle/x.js ... ] > bundle/common.js

Read `module-deps` json output from stdin, factoring each entry file out into
the corresponding output file (-o).

If there is a trailing unpaired `-o`, that file will be used for the common
bundle output. Otherwise, the final bundle is written to stdout.

var factor = require('factor-bundle')

Return a transform stream tr that factors the array of entry path strings files out into bundle files. The input format that fr expects is described in the module-deps package.

The output format for fr and each of the fr sub-streams given by each 'stream' event is also in the module-deps format.

The files held in common among > opts.threshold (default: 1) bundles will be output on the fr stream itself. The entry-specific bundles are diverted into each 'stream' event's output. opts.threshold can be a number or a function opts.threshold(row, groups) where row is a module-deps object and groups is an array of bundles which depend on the row. If the threshold function returns true, that row and all its dependencies will go to the common bundle. If false, the row (but not its dependencies) will go to each bundle in groups. For example:

factor(files, {threshold: function(row, groups) {
    if (/.*a\.js$/.test(row.id)) return false;
    if (/.*[z]\.js$/.test(row.id)) return true;
    return this._defaultThreshold(row, groups);
}});

Each entry file emits a 'stream' event containing all of the entry-specific rows that are only used by that entry file (when opts.threshold === 1, the default).

The entry file name is available as stream.file.

With npm do:

npm install factor-bundle

MIT