call方法来源网络原文链接

简单理解call方法

//例1
window.color = 'red';
document.color = 'yellow';

var s1 = {color: 'blue' };
function changeColor(){
    console.log(this.color);
} 
//执行结果
changeColor.call();         //red (默认传递参数)
    changeColor.call(window);   //red
    changeColor.call(document); //yellow
    changeColor.call(this);     //red
    changeColor.call(s1);       //blue



//例2
var Pet = {
    words : '...',
    speak : function (say) {
        console.log(say + ''+ this.words)
    }
}
Pet.speak('Speak'); // 执行结果：Speak...

var Dog = {
    words:'Wang'
}

//将this的指向改变成了Dog
Pet.speak.call(Dog, 'Speak'); //执行结果： SpeakWang

来源网络原文链接