call和apply的使用

call和apply的第一个参数都是待绑定的对象，第二个参数有差别

//call使用的参数是可变参数
//apply使用的参数是数组
function sum() {
var result = 0;
for (var i = 0; i < arguments.length; i++) {
result += arguments[i];
}
return result;
}

function Obj(x, y) {
this.x = x;
this.y = y;
}

var obj = new Obj(10, 20); //这种方式就是把函数指向交给了obj

var result = sum.call(obj, obj.x, obj.y);

var result2 = sun.apply(obj, [obj.x, obj.y]);
console.log(result);

console.log(result2);

var teacher = {name: ‘mr.zhao‘};

function showName() {
console.log(this.name);
}

showName.call(student);
showName.call(teacher);

function Animal() {
this.hoal = function() {
console.log("aaa");
}
}

function Cat() {
Animal.call(this);
}

var cat = new Cat();
cat.hoal();

function Tiger() {
Cat.apply(this);
}

var tiger = new Tiger();
tiger.hoal();

function sum() {
var result = 0;
for (var i = 0; i < arguments.length; i++) {
result += arguments[i];
}
return result;
}

function Obj(x, y) {
this.x = x;
this.y = y;
}
//简单的call的模拟
sum.mycall = function(obj) {
if (arguments.length == 0) {
console.log("必须传入一个绑定对象");
} else {
return this(arguments[1], arguments[2]);
}
}
console.log(sum.mycall(obj, obj.x, obj.y));