JavaScript-Object函数

JavaScript 函数是引用类型 (对象类型) 所以 Function 函数也是对象

"Function 构造函数" 也是一个对象，所以也有 __proto__ 属性

"Function 构造函数" 的 __proto__ 属性指向 "Function 原型对象"

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Demo</title>
    <script type="text/javascript">
        function Person(name, age) {
            this.name = name;
            this.age = age;
        }

        let obj = new Person("BNTang", 28);
        console.log(Function.__proto__);
        console.log(Function.__proto__ === Function.prototype);
    </script>
</head>
<body>
</body>
</html>

JavaScript 中还有一个系统提供的构造函数叫做 Object

只要是函数都是 "Function 构造函数" 的实例对象

只要是对象就有 __proto__ 属性，所以 "Object 构造函数" 也有 __proto__ 属性

"Object 构造函数" 的 __proto__ 属性指向创建它那个构造函数的 "原型对象"

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Demo</title>
    <script type="text/javascript">
        function Person(name, age) {
            this.name = name;
            this.age = age;
        }

        let obj = new Person("BNTang", 28);
        console.log(Object);
        console.log(Object.__proto__);
        console.log(Object.__proto__ === Function.prototype);
    </script>
</head>
<body>
</body>
</html>

只要是构造函数都有一个默认的属性，叫做 prototype

prototype 属性保存着一个对象，这个对象我们称之为 "原型对象"

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Demo</title>
    <script type="text/javascript">
        function Person(name, age) {
            this.name = name;
            this.age = age;
        }

        let obj = new Person("BNTang", 28);
        
        console.log(Object.prototype);
    </script>
</head>
<body>
</body>
</html>

只要是原型对象都有一个默认的属性，叫做 constructor

constructor 指向当前原型对象对应的那个 "构造函数"

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Demo</title>
    <script type="text/javascript">
        function Person(name, age) {
            this.name = name;
            this.age = age;
        }

        let obj = new Person("BNTang", 28);

        console.log(Object.prototype.constructor);
        console.log(Object.prototype.constructor === Object);
    </script>
</head>
<body>
</body>
</html>

object 函数的注意点，object 的 __proto__ 是指向 null

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Demo</title>
    <script type="text/javascript">
        function Person(name, age) {
            this.name = name;
            this.age = age;
        }

        let obj = new Person("BNTang", 28);
        
        console.log(Object.prototype.__proto__);
    </script>
</head>
<body>
</body>
</html>