如何使用给定的原型链创建对象？

Question

I need a way to create an empty object whose prototype chain is provided as an array of objects:

var prototypes = [{one: 1}, {two: 2}, {three: 3}];
var created = create(prototypes);
// prototype chain of created should be:
// created --> {one: 1} --> {two: 2} --> {three: 3}

How can I do this?

Answer 1

You basically can't (currently*), because there is only one prototype chain, prototypes are currently assigned only at object creation, and yet you have multiple discrete objects there that are unrelated. That is, to create the chain, you need each object in the chain to be backed by the previous one, but those aren't.

What you can do is create the chain with copies of those objects, but of course subsequent changes to those original objects wouldn't be reflected in the chain.

You can get close with ECMAScript5 by creating new objects with getters and setters for all of the existing properties on those source objects and syncing them, but that wouldn't handle new properties (or deleted ones), just changes to existing properties.

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* I said "currently" above because the current draft specification for the next ECMAScript version, ECMAScript 6th Edition, has a new Reflect object which has the ability to set a prototype on an existing object retrospectively. (Whereas with ECMAScript5 and earlier, you can only set an object's prototype when you're creating it.) So as of ES6, you'd be able to assemble those objects into a chain by using the future Reflect.setPrototypeOf method. But right now, cross-browser, you can't.