babel-plugin-replace-object-assign

Replaces Object.assign with a polyfill.

Also, this plugin will import an external package in files where Object.assign is used rather than redeclaring the function in each file (which should help reduce bundle size). This is ultimately what babel-plugin-transform-runtime does for you when using the _extends helper.

The implementation you configure is specified as a npm package dependency.

⚠️ Important note on the use of this project:

Most likely you do not and should not use this plugin! I initially wrote this plugin due to a bug in Chrome where key order was not gaurenteed to be correct for objects mutated with Object.assign (the issue is also described at sindresorhus/object-assign#22).

While the bug did not cause problems for most projects, it did causes problems for a project I was helping maintain (Material-UI). We heavily used Object.assign to merge style definitions that were defined in javascript objects. Since key order is important when defining CSS style rules, the Object.assign implementation built into Chrome caused many style related bugs. This plugin allowed us to completely replace all uses of Object.assign within our source code with an implementation that did not break in Chrome (with the expectation that we would stop using this plugin when the bug was fixed and rolled out to a majority of Chrome users).

The bug in Chrome has been fixed for quite some time now (it was fixed in Chrome 49), so this plugin is no longer necessary for the purpose it was originally created for. We have also stopped using this plugin for Material-UI. Please carefully consider the necessity and implications of replacing all of your Object.assign calls before using this plugin. If you are not sure if you need this, feel free to open an issue to discuss it.

Usage

Installation

# Install the plugin
$ npm install babel-plugin-replace-object-assign

Configure

.babelrc

{
  "plugins": [
    ["replace-object-assign"]
  ]
}

Result

In

Object.assign(a, b);

Out

var _objectAssign2 = function(target) {
    for (var i = 1; i < arguments.length; i++) {
        var source = arguments[i];

        for (var key in source) {
            if (Object.prototype.hasOwnProperty.call(source, key)) {
                target[key] = source[key];
            }
        }
    }

    return target;
};

_objectAssign(a, b)