ES6 Class里面的this对象

class Person {
    constructor(name){
        this.name =name
    }
    says(some){
        setTimeout(function(){
            console.log(this.name+ ' says ' + some)
        }, 1000)
    }
    //第一种是将this传给self,再用self来指代this
    says1(some){
        var self = this;
        setTimeout(function(){
            console.log(self.name+ " says1 " +some);
        },1000)
    }
    //第二种方法是用bind(this),即
    says2(some){
        setTimeout(function(){
            console.log(this.name+ " says2 " + some);
        }.bind(this),1000);
    }
    //第三种方法是箭头函数
    says3(some){
        setTimeout( () => {
            console.log(this.name+ ' says3 ' + some)
        }, 1000)
    }
}
 
 var p1 = new Person("GG")
 p1.says('hi')  //undefined says hi
 p1.says1('hi')  //GG says1 hi
 p1.says2('hi')  //GG says2 hi
 p1.says3('hi')  //GG says3 hi