How to set a prototype for a JSON object?

问题:

I am receiving some JSON object from the server, and I want to 'typecast' or 'bless' it to an object with already defined methods. Is there any way to set a prototype for a plain JSON object?

function MyClass(someValue) {
    this.myProperty = someValue;
}

MyClass.prototype.someMethod = function() { return "Here's " + this.myProperty + "!"};

var json = {myProperty : 'someValue'};

// ??? json.prototype = MyClass doesn't work, of course.

var result = json.someMethod();

How can I do that?

回答1:

Well, I can suggest to try out these:

• By adding the needed functions to ALL Javascript objects (bad practice)

  Object.prototype.lol = function() { alert(this.a); };
  var x = {a : 'b'};
  x.lol();
  

• By "extending" JSON with a function:

  var json = {a : 'b', b : 123};
  function extend(obj) {
      obj.func1 = function(param) {
          alert(this[param]);
      }
  }
  extend(json);
  json.func1('b');
  

• By "making" the object into a function:

  var json = {a : 'b', b : 123};
  function extendToFunc(obj) {
      var theLibrary = function(obj) {
          /**
           * The same as above.
          */
          this.func1 = function(param) {
               alert(obj[param]);
          }
      };
      return new theLibrary(obj);
  }
  var jsonFunc = extendToFunc(json);
  jsonFunc.func1('b');
  

Or you can use a JS framework for that. Or any other method that you can think of :) My examples are easy, they can be extended into anything sophisticated you need.

回答2:

OK. Here is the answer (which is IE-incompatible):

json.__proto__ = MyClass.prototype;

Thankfully, I don't need no %$@$%# IE in my application.

(When I do, there is another possibility: create a wrapper function in MyClass prototype which copies all properties from JSON to the new object; shallow-copying should be enough).