使JSON.parse创建的对象继承自另一个类

Question

I receive a bunch of objects via JSON which ultimately need to have some instance member functions.

Is there a way to do this without copying the data?

For example:

var DataObject = function() {};
DataObject.prototype.add = function() { return this.a + this.b; };

var obj = JSON.parse('{"a":1, "b":2}');

// Do something to obj to make it inherit from DataObject

console.assert( obj.add() === 3 );

I've tried setting obj.prototype = DataObject.prototype but that doesn't seem to work. What am I missing?

Answer 1

Well, in ECMAScript6 (in IE11, and every other non ie browser today), that would be __proto__

obj.__proto__ = Object.create(DataObject.prototype);

[ fiddle ]

Generally, make sure you only do this at the object creation case, otherwise it can be very risky to do.

Also note, setting the protoype explicitly is not always faster than copying two properties, as you can see here so you have to be sure there is actual gain here.