javascript 一些函数的实现 Function.prototype.bind, Array.prototype.map

* Function.prototype.bind

Function.prototype.bind = function() {
	var self = this,
		context = [].shift.call(arguments),
		args = [].slice.call(arguments);
	return function() {
		return self.apply(context, [].concat.call(args, [].slice.call(arguments)));
	}
}

　// test

// test
var obj = {
	name: 'mingzhanghui'
};
var func = function(a, b, c, d) {
	console.log(this.name);
	console.log([a,b,c,d]);
}.bind(obj, 1, 2);

func(3,4);

　　

* Array.prototype.map

Array.prototype.map = function(callback) {

	var T, A, k;
	if (this == null) {
		throw new TypeError('this is null or not defined');
	}
	var O = Object(this);
	var len = O.length >>> 0;

	if (typeof callback !== 'function') {
		throw new TypeError(callback + ' is not a function');
	}
	if (arguments.length > 1) {
		T = arguments[1];
	}
	A = new Array(len);
	k = 0;

	while (k < len) {
		var kValue, mappedValue;
		if (k in O) {
			kValue = O[k];
			mappedValue = callback.call(T, kValue, k, O);
			A[k] = mappedValue;
		}
		k++;
	}
	return A;
};