JavaScript常見面試題

1.考點:閉包

var name = "window"
var obj = {
    name: "obj", 
    func:function(){
         return function(){
         return console.log(this.name)
     }
  }  
}
obj.func()()  // window

var name = "window"
var obj = {
    name: "obj", 
    func:function(){
    var self = this
         return function(){
         return console.log(self.name)
     }
  }  
}
obj.func()()  // obj

2.考點：閉包、js異步任務隊列

for (var i = 0; i < 5; i++) {
	(function(i) {
		setTimeout(() => {
			console.log(i)
		}, 1000)
	})(i)
}
console.log(i)

先輸出5,1秒後輸出0，1，2，3，4
3.考點：原型鏈的公有屬性、原型屬性、靜態屬性與繼承

var Animal = function() {
		this.price = 3000
	}
var Dog = function() {}
Dog.price = 2000
Animal.prototype.price = 1000
Dog.protoType = new Animal()
var dog = new Dog()
console.log(dog.price) // 3000

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