Popular posts

This is the formatted code.

function extend(obj, id) {
     obj.toObject = (function(toObject) {
                         return function() {
                                    return fabric.util.object.extend(toObject.call(this), {id: id});
                              };
                    })(obj.toObject);

}

Now lets simplify it..

Core method

fabric.util.object.extend(toObject.call(this), {id: id}); //some fabric lib specific method

Now,

function extend(obj, id) {
    obj.toObject = (somefunction(toObject))(obj.toObject);
}

An IIFE expression which executes when obj.toObject is initiated.obj.toObject object is passed to somefunction()

Now this IIFE is returning an closure.

return fabric.util.object.extend(toObject.call(this), {id: id});.

So basically your function will assigntoObject function to any object passed to extend