add lexical this, args, and return

[sezgi]

add arrow fn to get lexical this for brevity; args for e.g. boundFn(5); return value of original fn

[sezgi]

For example:

Function.prototype.bind = function(context) {
    return (...args) => {
        return this.apply(context, args);
    }
}

let foo = {
    base: 3,
    myFunc(num) {
        return this.base + num;
    }    
}

let newFunc = foo.myFunc.bind({base: 6});
console.log('old', foo.myFunc(5));
console.log('new', newFunc(5));