從MDN文檔中獲取標準 setPrototypeOf功能以及非標準 __proto__財產(chǎn):改變對象的[原型]，無論這是如何實現(xiàn)的，都是強烈的勸阻，因為在現(xiàn)代JavaScript實現(xiàn)中，它非常緩慢，不可避免地減緩了后續(xù)的執(zhí)行。使用Function.prototype添加屬性是這個將成員函數(shù)添加到j(luò)avascript類的方法。然后如下所示：function Foo(){}function bar(){}var foo = new Foo();// This is bad: //foo.__proto__.bar = bar;
// But this is okayFoo.prototype.bar = bar;// Both cause this to be true: console.log(foo.__proto__.bar == bar); // true為什么foo.__proto__.bar = bar;壞的?如果不是壞事Foo.prototype.bar = bar;同樣糟糕？那么為什么這個警告：在現(xiàn)代JavaScript實現(xiàn)中，它非常慢，不可避免地減緩了后續(xù)的執(zhí)行。..當然Foo.prototype.bar = bar;也沒那么糟。更新也許他們所說的突變意味著重新分配。見已接受的答案。
function Constructor(){
if (!(this instanceof Constructor)){
return new Constructor();
} }Constructor.data = 1;Constructor.staticMember = function(){
return this.data;}Constructor.prototype.instanceMember = function(){
return this.constructor.data;}Constructor.prototype.constructor = Constructor;
// By doing the following, you are almost doing the same as assigning to
// __proto__, but actually not the same :Pvar newObj = Object.create(Constructor);
// BUT newObj is now an object and not a // function like !!!Constructor!!!
// (typeof newObj === 'object' !== typeof Constructor === 'function'), and you
// lost the ability to instantiate it, "new newObj" returns not a constructor,
// you have .prototype but can't use it. newObj = Object.create(Constructor.prototype);
// now you have access to newObj.instanceMember // but staticMember is not available. newObj instanceof Constructor is true
// we can use a function like the original constructor to retain // functionality, like self invoking it newObj(), accessing static
// members, etc, which isn't possible with Object.createvar newObj = function(){
if (!(this instanceof newObj)){
return new newObj();
}}; newObj.__proto__ = Constructor;newObj.prototype.__proto__ = Constructor.prototype;newObj.data = 2;(new newObj()).instanceMember();
//2newObj().instanceMember(); // 2newObj.staticMember(); // 2newObj() instanceof Constructor; // is trueConstructor.staticMember();
// 1
