binding both "this" object and optionally arguments

bind.js

// binding both "this" object and optionally arguments

if (!Function.prototype.bind) {
    Function.prototype.bind = function bind(thisObject) {
        var fun = this, boundArgs = Array.prototype.slice.call(arguments, 1);
        return function() {
            var allArgs = boundArgs;
            if (arguments.length) {
                allArgs = allArgs.concat(Array.prototype.slice.call(arguments));
            }
            fun.apply(thisObject, allArgs);
        };
    };
}

test.js

// run it with `node test.js`
require('./bind.js')

function buy(what) {
    console.log(this.name + " is goint to buy " + what);
}

var blake = {
    name: 'William Blake',
    occupation: 'painter'
};

var blakeBuys = buy.bind(blake);
var blakeBuysOranges = buy.bind(blake, 'oranges');

var caesar = {
    name: 'Julius Caesar',
    occupation: 'emperor'
};

var caesarBuysSoldiers = buy.bind(caesar, 'soldiers');

buy();
blakeBuys();
blakeBuys('a car');
blakeBuysOranges();
caesarBuysSoldiers();