一、call 方法
基本用法

function test() {console.log('hello world');
}
test(); // hello world
test.call(); // hello world
// test() ==> test.call()

其实就是借用别人的方法，来实现自己的功能

function Person(name, age) {// this == objthis.name = name;this.age = age;
}var obj = {};var person = new Person();
Person.call(obj, 'mary', 18); // 让 obj 也拥有构造函数的方法

call 的根本作用就是改变 this 指向，第一个参数就是 this 的指向

小案例

function Student(name, age, sex) {this.name = name;this.age = age;this.sex = sex;
}function Color(red, blue, pink) {this.red = red;this.blue = blue;this.pink = pink;
}function Model(height, width, len) {this.height = height;this.width = width;this.len = len;
}function Car(name, age, sex, red, blue, pink, height, width, len) {// var this = {//     // };Student.call(this, name, age, sex);Color.call(this, red, blue, pink);Model.call(this, height, width, len);
}var car = new Car('mary', 18, 'female', 'red', 'blue', 'pink', 175, 75, 175);

二、apply 方法

function Student(name, age, sex) {this.name = name;this.age = age;this.sex = sex;
}function Color(red, blue, pink) {this.red = red;this.blue = blue;this.pink = pink;
}function Model(height, width, len) {this.height = height;this.width = width;this.len = len;
}function Car(name, age, sex, red, blue, pink, height, width, len) {// var this = {//     // };Student.apply(this, [name, age, sex]);Color.apply(this, [red, blue, pink]);Model.call(this, height, width, len);
}var car = new Car('mary', 18, 'female', 'red', 'blue', 'pink', 175, 75, 175);

1. call 需要把实参按照形参的个数传进去
2. apply 需要传一个 arguments 实参列表

[].slice.call(arguments) -- 能将具有 length 属性的对象转换为数组

三、总结

call / apply 都是改变 this 指向，区别就是传参列表不同