关于html:第-38-题applycall-和-bind-是什么哪些区别

5次阅读

共计 1597 个字符，预计需要花费 4 分钟才能阅读完成。

三者都是扭转 this 指向的 api

apply：xxx.apply(this, [arg1, arg2])

call：xxx.call(this, arg1, arg2)

bind：xxx.bind(this, arg1, arg2)

次要是传参形式和执行形式不同

apply、call 的区别：承受参数的形式不一样
bind：不立刻执行。而 apply、call 立刻执行

初始状态

let Person = function(name, age) {
    this.name = name;
    this.age = age;
};

let Student = function() {
    this.class = 'classA';

    this.run = function() {console.log(this);
    };
};

let student = new Student();

student.run();

能够看见这个时候打印的 this 是指向 Student 构造函数，并且和 Person 构造函数没有任何关联

let Person = function(name, age) {
    this.name = name;
    this.age = age;
};

let Student = function() {
    this.class = 'classA';

    this.run = function() {Person.apply(this, ['xiaoming', 20]);
        console.log(this);
    };
};

let student = new Student();

student.run();

这个时候 this 曾经指向了 Person 构造函数了

let Person = function(name, age) {
    this.name = name;
    this.age = age;
};

let Student = function() {
    this.class = 'classA';

    this.run = function() {Person.call(this, 'xiaoming', 20);
        console.log(this);
    };
};

let student = new Student();

student.run();

这个时候 this 曾经指向了 Person 构造函数了

let ex = '';

let Person = function(name, age) {
    this.name = name;
    this.age = age;
};

let Student = function() {
    this.class = 'classA';

    this.run = function() {ex = Person.bind(this, 'xiaoming', 20);
        console.log(this);
    };
};

let student = new Student();

student.run();
ex();

应用 bind 的话，须要执行了 this 扭转才会失效

总结：应用 apply、call 和 bind 的确能够扭转 this 指向，然而原有对象的属性也跟着一起过来了