我们需要关注内置构造函数的prototype，
1、三个包装类对象
Number.prototype
Number {0, constructor: ƒ, toExponential: ƒ, toFixed: ƒ, toPrecision: ƒ, …}
String.prototype
String {"", constructor: ƒ, anchor: ƒ, big: ƒ, blink: ƒ, …}
Boolean.prototype
Boolean {false, constructor: ƒ, toString: ƒ, valueOf: ƒ}2、数组
Array.prototype
[constructor: ƒ, concat: ƒ, copyWithin: ƒ, fill: ƒ, find: ƒ, …]3、对象
Object.prototype
{constructor: ƒ, __defineGetter__: ƒ, __defineSetter__: ƒ, hasOwnProperty: ƒ, __lookupGetter__: ƒ, …}4、函数
Function.prototype
ƒ () { [native code] }