JS中的prototypeproto与constructor

1. 寻找原型

心法口诀：每个对象的原型(__proto__)都指向自身的构造函数(constructor)的prototype属性

let b={}b.constructor === Object// trueb.__proto__ === Object.prototype// trueb.__proto__ === b.constructor.prototype// true

1. 所以想要知道某个对象的原型是什么，首先找到他的构造函数是什么

9个终极类

Array.constructor// ƒ Function() { [native code] }Boolean.constructor// ƒ Function() { [native code] }Date.constructor// ƒ Function() { [native code] }Number.constructor// ƒ Function() { [native code] }String.constructor// ƒ Function() { [native code] }Object.constructor// ƒ Function() { [native code] }RegExp.constructor// ƒ Function() { [native code] }Symbol.constructor// ƒ Function() { [native code] }

1个究极类

Function.constructor// ƒ Function() { [native code] }

3中特殊数字对象

Math.constructor// ƒ Object() { [native code] }// Math 对象并不像 Date 和 String 那样是对象的类，因此没有构造函数 Math()NaN.constructor// ƒ Number() { [native code] }Infinity.constructor// ƒ Number() { [native code] }

2中bug类型

undefined.constructor// VM25366:1 Uncaught TypeError: Cannot read property 'constructor' of undefined at <anonymous>:1:11null.constructor// VM25366:1 Uncaught TypeError: Cannot read property 'constructor' of null at <anonymous>:1:11

...