1、原型链继承

function Parent() {
    this.name = 'Mike'
}
function Child() {
    this.age = 12;
}
Child.prototype = new Parent();//Child继承Parent，通过原型，形成链条

var test = new Child();
console.log(test.age);
console.log(test.name);//得到被继承的属性

//继续原型链继承
function Brother() {//brother构造
    this.weight = 60;
}
Brother.prototype = new Child();//继续原型链继承
var brother = new Brother();
console.log(brother.name);
console.log(brother.age);