javascript学习:闭包和prototype原型使用基础

时间:2021-09-07 16:59:45

闭包

function Person(name) {
this.Username = name;
var Userage = 18; //通过这种方法可以模拟私有成员
//类似于private成员
this.setAge = function (age) {
Userage = age;
}
//类似于public成员
this.getAge = function () {
return Userage;
}
}
var p1 = new Person("huahuah");
p1.setAge(100); alert(p1.getAge())
//------------------------------------------------- var x = 100;
//执行3 找到x定义
function f1() {
var y = 101;
//执行2,找到x未定,继续找
alert(y);
alert(x);
//整个return函数就是常说的闭包
//由此函数开始执行1,找不到x
//闭包靠的是作用域链作用的,必须一层一层释放
return function () {
var y = 99;
alert(x);
alert(y);
//向上找
}
}
function f1() {
var funs = new Array();
//2:找到i,但是i已经循环遍历了i=10
for (var i = 0; i < 10; i++) {
//1:先执行闭包内,找不到i,搜索外层
funs[i] = function () {
alert(i);
}
}
//3:返回i=10
return funs;
}
//4:声明myfuns=f1()
var myfuns = f1(); for (var n = 0; n < myfuns.length; n++) {
//5:因为f1的长度=10,所以n的长度也=10,循环遍历弹出n的值
myfuns[n]();
}

原型:

//prototype原型
function Person(name, age, email) {
this.UserName = name;
this.UserAge = age;
this.UserEmail = email;
this.sayHi=function(){
alert('你好,我的名字是' + this.UserName + '今年' + this.UserAge + '岁了' + '我的联系邮箱是' + this.UserEmail); }
this.sayHellp= function () {
alert()
}
}
//通过构造函数创建的对象 都是完全独立的对象 对象与对象之间是没有关系的,类似c#中的对象
var p1 = new Person("黄", "18", "595892312@qq.com");
p1.sayHi();
var p2 = new Person("huang", "23", "123@163.com");
alert('~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~');
p2.sayHi();
p1.UserName = "zhen";
p1.UserAge = 15;
p1.UserEmail = "854658496@sina.com";
p1.sayHi(); ///////////////////////////原型2
//定义构造函数
function Person(name, age, email) {
this.UserName = name;
this.UserAge = age;
this.UserEmail = email;
}
//_proto_
//prototype是person对象的原型对象
//在person的原型对象中加一个sayHi()方法
Person.prototype.sayHi = function () {
alert("My name is" + this.UserName + "," + this.UserAge + "old,My Email is" + this.UserEmail);
}
//通过构造函数创建函数对象
var p1 = new Person("susan", 18, "suan@gogle.com");
p1.sayHi();
var p2 = new Person("黄", 23, "5231@qq.com");
p2.sayHi(); ////////////////通过原型实现扩展方法
//给字符串对象原型添加haha方法
String.prototype.haha=function (){
return this+"☆";
};
//创建字符串对象
var msg = '56465455645';
msg = msg.haha();
alert(msg); ///通过原型prototype实现继承
//js中没有类的概念,继承是通过对象和对象来实现的
function Person(name,age,email) {
this.Username = name;
this.Userage = age;
this.Useremail = email;
}
Person.prototype.sayHi = function () {
alert("我的名字叫做" + this.Username + "今年" + this.Userage + "岁了,我的邮箱是:" + this.Useremail);
};
//student
function Student(sid) {
this.student_id = sid;
}
//继承 通过prototype=p1继承Person中的属性
Student.prototype = new Person("黄", 18, "huang@163.com");
var s1 = new Student('1564156165');
s1.Username = '李'; alert(s1.Username);