Fix property assignment on WebKit

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1801.4.18 years ago8 years agoMinified + gzip package size for webkit-assign in KB


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Due to WebKit issue #138038, assigning to a property of an object created with Object.create may result in the error `TypeError: Attempted to assign to readonly property.`. This bug is known to affect iOS 8 users and is likely to occur in recent versions of Angular.js and PDF.js.
This utility rewrites the following code
object.$$a = 5;

to this
var __webkitAssign__$$a = "$$a";
object[__webkitAssign__$$a] = 5;

as a workaround to prevent a TypeError.


webkit-assign provides a CLI interface (when installed globally via `npm i -g webkit-assign`). Specify any number of files, and each one will be transformed and saved to a file with a .webkitassign.js extension in the same directory.
For instance, the below command produces a transformed version of angular.js with the name angular.webkitassign.js in the same directory:
$ webkit-assign angular.js

In Node.js, you can require webkit-assign (when installed locally via `npm i webkit-assign`), and pass code to the module as a string:
var fs = require('fs');
var webkitAssign = require('webkit-assign');
var original = fs.readFileSync('node_modules/angular/angular.js', 'utf8');
var transformed = webkitAssign(original);
fs.writeFileSync('build/scripts/angular.js', code);

You can also obtain a transform stream by calling webkitAssign() (without any arguments), and pipe code through it:
var fs = require('fs');
var webkitAssign = require('webkit-assign');


We offer several plugins, all hosted in this repository.
A gulp plugin:
var gulp = require('gulp');
var webkitAssign = require('webkit-assign/gulp');

A Browserify transform:
"browserify": {
  "transform": [

A Webpack loader:
loaders: [
    test: /angular\.js$/,
    loader: 'webkit-assign/webpack'


Install the module locally via git:
$ git clone https://github.com/StoryCloud/webkit-assign.git
$ cd webkit-assign
$ npm install
$ npm link

Please provide unit tests and documentation for any changes. Try to maintain existing formatting and naming conventions. You can check your code with `npm test`.