Prototype, Constructor的施用和理解 _Web前端

Prototype, Constructor的使用和理解
JavaScript中Prototype的使用和实例
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<script>
(function(){
	console.log("=========prototype的用法和误区=========");
	var A = function(){};
	A.prototype.A1 = function(){
		console.log("A1");
	};
	A.prototype.A2 = [1,2,3];
	A.prototype.A3 = 1;
	var a1 = new A();
	var a2 = new A();
	a1.A2.push(4);
	a1.A3 = 2;
	console.log(a1.A3);//2
	console.log(a2.A3);//1
	console.log(a1.A2);//[1,2,3,4]
	console.log(a2.A2);//[1,2,3,4]
	/**
	由于prototype是模版不是对象拷贝而是链接的方式
	所以使用delete a1.A3, a1.A3并不会删除， 而是重新链上上一个值
	**/
	delete a1.A3;
	console.log(a1.A3);//1
	console.log(a2.A3);//1
	delete a1.A2;
	console.log(a1.A2);
	console.log("=========以下是继承部分=========");
	var B = function(){};
	B.prototype = new A();
	B.prototype.A3 = 10;
	var b1 = new B();
	console.log(b1.A3);//[1,2,3,4]
	console.log("=========以下是constructor部分=========");
	var C = function(){};
	C.prototype = {
		C1 : function(){}
	};
	var c = new C();
	console.log(a1.constructor ===A);//true
	/**
	C.prototype = {
		C1 : function(){}
	};
	等同于:
	C.prototype = new Object({
		C1 : function(){}
	});
	所以: c.constructor===C 为 false
	**/
	console.log(c.constructor===C);//false
	console.log(c.constructor===Object);//true
	console.log(C.prototype.constructor===Object);//true
})();
</script>