How to use js objects and prototypes
This time I will show you how to use js objects and prototypes, and what are the precautions for using js objects and prototypes. The following is a practical case, let's take a look.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>title</title>
<script>
/*
*
* 复习:
*
* 面向过程和面向对象都是编程的思想,方式不一样
* 面向过程:凡事都是亲力亲为,所有的代码都要自己写,每一步都要很清楚,注重的是过程
* 面向对象:执行者成为指挥者,只要找对象,然后让对象做相关的事情,注重的是结果
* 面向对象的特性:封装,继承,多态
* 封装；就是代码的封装,把一些特征和行为封装在对象中.
*
面向对象的编程思想
:根据需求,抽象出相关的对象,总结对象的特征和行为,把特征变成属性，行为变成方法,然后定义(js)
构造函数
,实例化对象,通过对象调用
属性和方法
,完成相应的需求.---编程的思想
*
* 对象:具体特指的某个事物,有特征(属性)和行为(方法)，对象可以看成是一坨无序属性的集合
*
* 如何
创建对象
?
* 通过调用new Object(),还有{},自定义构造函数
*
* 创建对象的方式
* 1. 调用系统Object()----->创建出来的对象都是Object类型的,不能很明确的指出这个对象是属于什么类型
* 2. 字面量的方式{}----->只能
创建一个对象
(一次只能创建一个)
*
* 3.
工厂模式
创建对象----->----->推论---->自定义构造函数的方式
* 自定义构造函数(优化后的工厂模式)
*
* 自定义构造函数创建对象:4件事
* 1.在内存中申请一块空闲的空间,存储创建的对象
* 2.this就是当前实例化的对象
* 3.设置对象中的属性和方法(为对象添加属性和方法,为属性和方法赋值)
* 4.把创建后的对象返回
* 都是需要通过new的方式
*
*
* 什么是原型?
* 构造函数中有一个属性prototype,是原型,程序员使用的
* 实例对象中有一个属性proto,是原型,浏览器使用的,不是很标准的,
* 实例对象中的proto指向的就是该实例对象中的构造函数中的prototype
* 构造函数中的prototype里面的属性或者方法,可以直接通过实例对象调用
* 正常的写法:实例对象.proto才能访问到构造函数中的prototype中的属性或者方法
* per.proto.eat();//proto不是标准的属性
* per.eat();
* 原型就是属性,而这个属性也是一个对象
* Person.prototype--->是属性
* Person.prototype.属性或者Person.ptototype.方法()
*
* 本身在构造函数中定义的属性和方法,当实例化对象的时候,实例对象中的属性和方法都是在自己的空间中存在的,如果是多个对象。这些属性和方法都会在单独的空间中存在,浪费内存空间,所以,为了数据共享,把想要节省空间的属性或者方法写在原型对象中,达到了数据共享，实现了节省内存空间
*
*
*
* 原型的作用之一:数据共享,节省内存空间
*
* 原型的写法:
* 构造函数.prototype.属性=值
* 构造函数.prototype.方法=值---->函数.prototype,函数也是对象,所以,里面也有proto
* 实例对象.prototype-------->实例对象中没有这个属性,只有proto(暂时的)
*
* 简单的原型的写法
* 缺陷:--->新的知识点---->原型直接指向{}---->就是一个对象,没有构造器
* 构造函数.prototype={
* 切记:如果这这种写法,要把构造器加上
*
* };
*
*
* 通过原型为内置对象添加原型的属性或者方法----->原因:
* 系统的内置对象的属性和方法可能不满足现在需求,所以,可以通过原型的方式加入属性或者方法,为了方便开发
*
* 为内置对象的原型中添加属性和方法,那么这个内置对象的实例对象就可以直接使用了
* String.prototype.方法=匿名函数;
* var str="哈哈";
* str.方法();---->实例对象可以直接调用原型中的属性或者方法
*
*
*
*
*
*
*
*
*
* */
function Person(age) {
this.age=age;
}
Person.prototype.sayHi=function () {
};
var p=new Person(10);
p.sayHi();
</script>
</head>
<body>
</body>
</html>I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!
Recommended reading:
Detailed explanation of JS framework library use cases
How to use native js to create a starry sky effect
The above is the detailed content of How to use js objects and prototypes. For more information, please follow other related articles on the PHP Chinese website!
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