For-of 循​​环默认迭代器函数

Question

Consider this simple generator function defined on Object.prototype :

Object.prototype.defineProperty(Object.prototype, 'pairs', {
    enumerable: false,
    * value( ) {
        for (const key in this)
            yield [ key, this[key] ];
} });

Of course, it could be used like this:

const object = { goats_teleported: 42 };

for (const [ key, value ] of object.pairs());

But I wonder if there any way to assign pairs function to object prototype, so it will be automaticly fired in for-of loop without explicit call; just like this:

for (const [ key, value ] of object);

Any ideas?

Answer 1

   Object.prototoype[Symbol.iterator] = function* pairs() {
     //...
   };

But be aware that this could cause side effects everywhere. This shouldn't be used in production (or at least, on your own risk ;)).

Answer 2

Put the generator on Object.prototype[Symbol.iterator] :

 Object.prototype[Symbol.iterator] = function* pairs() { for (const key in this) yield [ key, this[key] ]; }; const object = { goats_teleported: 42, foo: 'fooval' }; for (const [ k, v ] of object) { console.log(k, v); }

Answer 3

in ES6 you can use Symbol.iterator to define custom iterator for prototype. See here