面试题_原型vs原型链

1. 最好画图

   function Fn() {
       this.x = 100;
       this.y = 200;
       this.getX = function () {
           console.log(this.x);
       }
   }
   Fn.prototype.getX = function () {
       console.log(this.x);
   };
   Fn.prototype.getY = function () {
       console.log(this.y);
   };
   let f1 = new Fn;
   let f2 = new Fn;
   console.log(f1.getX === f2.getX);
   console.log(f1.getY === f2.getY);
   console.log(f1.__proto__.getY === Fn.prototype.getY);
   console.log(f1.__proto__.getX === f2.getX);
   console.log(f1.getX === Fn.prototype.getX);
   console.log(f1.constructor);
   console.log(Fn.prototype.__proto__.constructor);
   f1.getX();
   f1.__proto__.getX();
   f2.getY();
   Fn.prototype.getY();
   

2. 一到经典的面试题

   function C1(name) {
       if (name) {
           this.name = name;
       }
   }
   function C2(name) {
       this.name = name;
   }
   function C3(name) {
       this.name = name || 'join';
   }
   C1.prototype.name = 'Tom';
   C2.prototype.name = 'Tom';
   C3.prototype.name = 'Tom';
   alert((new C1().name) + (new C2().name) + (new C3().name));
   

3. 计算输出的结果

   function Fn(num) {
   	this.x = this.y = num;
   }
   Fn.prototype = {
   	x: 20,
   	sum: function () {
   		console.log(this.x + this.y);
   	}
   };
   let f = new Fn(10);
   console.log(f.sum === Fn.prototype.sum);
   f.sum();
   Fn.prototype.sum();
   console.log(f.constructor);
   

4. 计算输出的结果

   function Fn() {
   	let a = 1;
   	this.a = a;
   }
   Fn.prototype.say = function () {
   	this.a = 2;
   }
   Fn.prototype = new Fn;
   let f1 = new Fn;
   
   Fn.prototype.b = function () {
   	this.a = 3;
   };
   console.log(f1.a);
   console.log(f1.prototype);
   console.log(f1.b);
   console.log(f1.hasOwnProperty('b'));
   console.log('b' in f1);
   console.log(f1.constructor == Fn);
   

5. 编写两个方法 plus / minus 实现如下的执行效果

   let n = 10;
   let m = n.plus(10).minus(5);
   console.log(m);//=>15（10+10-5）
   

6. 阿里超经典面试题

   function Foo() {
       getName = function () {
           console.log(1);
       };
       return this;
   }
   Foo.getName = function () {
       console.log(2);
   };
   Foo.prototype.getName = function () {
       console.log(3);
   };
   var getName = function () {
       console.log(4);
   };
   function getName() {
       console.log(5);
   }
   Foo.getName();
   getName();
   Foo().getName();
   getName();
   new Foo.getName();
   new Foo().getName();
   new new Foo().getName();
   

7、输出下面代码运行结果

//example 1
var a={}, b='123', c=123;  
a[b]='b';
a[c]='c';  
console.log(a[b]);

---------------------
//example 2
var a={}, b=Symbol('123'), c=Symbol('123');  
a[b]='b';
a[c]='c';  
console.log(a[b]);

---------------------
//example 3
var a={}, b={key:'123'}, c={key:'456'};  
a[b]='b';
a[c]='c';  
console.log(a[b]);

8、输出结果

function Foo() {
    Foo.a = function() {
        console.log(1)
    }
    this.a = function() {
        console.log(2)
    }
}
Foo.prototype.a = function() {
    console.log(3)
}
Foo.a = function() {
    console.log(4)
}
Foo.a();
let obj = new Foo();
obj.a();
Foo.a();