CKEDITOR.tools.createClass is unable to overwrite members

[jacekbogdanski]

Type of report

Bug

Provide detailed reproduction steps (if any)

1. Open IE8 with CKEditor4 sample page e.g. https://ckeditor.com/latest/samples
2. Open console.
3. Execute script:

var CreateClass = CKEDITOR.tools.createClass( {
	$: function() {
		this.message = 'Message from CreateClass!';
	},
	proto: {
			toString: function() {
				return this.message;
			},
		}
} );

function NativeClass () {
	this.message = 'Message from Native class!';
}

NativeClass.prototype.toString = function() {
	return this.message;
}

console.log( 'CreateClass', new CreateClass().toString() );
console.log( 'NativeClass', new NativeClass().toString() );

Expected result

In both console logs, you can see overwritten toString methods.

Actual result

Console log for the class created using CKEDITOR.tools.createClass prints [object Object] which means that the toString method has not been overwritten.

Other details

It may be related only to the native members.

• CKEditor version: from implementation

[jacekbogdanski]

The issue is caused by CKEDITOR.tools.extend method used internally by this function which doesn't support DontEnum attribute.