1. What is JavaScript
- JavaScript ("JS" for short) is a lightweight, interpreted or just-in-time compiled programming language with function first. Although it is famous as a scripting language for developing Web pages, it is also used in many non-browser environments. JavaScript is based on prototype programming, a multi-paradigm dynamic scripting language, and supports object-oriented, imperative, declarative, functional programming paradigm.
2. What is prototype and prototype chain, and what is the difference
- First, the prototype (prototpe): is specific to the function
- Second, the prototype chain ([[prototype]]): all data has
- 3. When the subclass attribute prototype (prototype) has no data, the attribute data of the prototype chain ([[prototype]]) will be mobilized until null is found. If there are no two, an error will be reported.
- Fourth, hasOwnProperty(): You can find out the private properties that only subclasses have
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<h2>原型与原型链</h2>
</body>
<script>
// 1、原型：prototype =>函数所特有的
// 2、原型链：[[prototype]] =>任何数据都有原型链
// 3、创建函数，绑定2个属性和1个方法
function Person() {
}
Person.prototype.name = 'jasmine'
Person.prototype.age = 18
Person.prototype.getAge = function () {
console.log(this.age)
}
// 4、创建一个Person实例对象,原型（prototype）的继承关系：继承属性和方法，进行调用
let person1 = new Person()
console.log(person1.name)
// 5、从当前实例属性原型(prototype)去查找,如果找了就返回(age=20),否则顺着原型链[[prototype]]一层一层往上找(age=18)
person1.age = 20
person1.getAge()
// 6、直到找到null为止,如果为null都没找到，则会报错
//person1.demo()
// 7、hasOwnProperty()=>仅子类有的私有属性，打印出来
person1.demo = 'demo'
let item;
for (item in person1) {
//
if (person1.hasOwnProperty(item)) {
console.log(item)
}
}
</script>
</html>
Code Analysis:
