Javascript: stringify object (including members of type function)

You can use JSON.stringify with a replacer like:

JSON.stringify({
   color: 'red',
   doSomething: function (arg) {
        alert('Do someting called with ' + arg);
   }
}, function(key, val) {
        return (typeof val === 'function') ? '' + val : val;
});

A quick and dirty way would be like this:

Object.prototype.toJSON = function() {
  var sobj = {}, i;
  for (i in this) 
    if (this.hasOwnProperty(i))
      sobj[i] = typeof this[i] == 'function' ?
        this[i].toString() : this[i];

 return sobj;

};

Obviously this will affect the serialization of every object in your code, and could trip up niave code using unfiltered for in loops. The "proper" way would be to write a recursive function that would add the toJSON function on all the descendent members of any given object, dealing with circular references and such. However, assuming single threaded Javascript (no Web Workers), this method should work and not produce any unintended side effects.

A similar function must be added to Array's prototype to override Object's by returning an array and not an object. Another option would be attaching a single one and let it selectively return an array or an object depending on the objects' own nature but it would probably be slower.

function JSONstringifyWithFuncs(obj) {
  Object.prototype.toJSON = function() {
    var sobj = {}, i;
    for (i in this) 
      if (this.hasOwnProperty(i))
        sobj[i] = typeof this[i] == 'function' ?
          this[i].toString() : this[i];

    return sobj;
  };
  Array.prototype.toJSON = function() {
      var sarr = [], i;
      for (i = 0 ; i < this.length; i++) 
          sarr.push(typeof this[i] == 'function' ? this[i].toString() : this[i]);

      return sarr;
  };

  var str = JSON.stringify(obj);

  delete Object.prototype.toJSON;
  delete Array.prototype.toJSON;

  return str;
}

http://jsbin.com/yerumateno/2/edit

Something like this...

(function(o) {
    var s = "";
    for (var x in o) {
        s += x + ": " + o[x] + "\n";
    }
    return s;
})(obj)

Note: this is an expression. It returns a string representation of the object that is passed in as an argument (in my example, I'm passing the in an variable named obj).

You can also override the toString method of the Object's prototype:

Object.prototype.toString = function() {
    // define what string you want to return when toString is called on objects
}

It's impossible without the help of the object itself. For example, how would you serialize the result of this expression?

(function () {
  var x; 
  return {
      get: function () { return x; },
      set: function (y) { return x = y; }
    };
})();

If you just take the text of the function, then when you deserialize, x will refer to the global variable, not one in a closure. Also, if your function closes over browser state (like a reference to a div), you'd have to think about what you want that to mean.

You can, of course, write your own methods specific to individual objects that encode what semantics you want references to other objects to have.

JSONfn plugin is exactly what you're looking for.

http://www.eslinstructor.net/jsonfn/

--Vadim

Perfectly stringify functions in objects by a replacer-argument in JSON.stringify(). The bad thing is that it puts apostrophes around the returned value. The apostrophes is impossible to know where to remove when the value is a function; like {"doSomething": "function(arg){...}"}. Instead return a PLACEHOLDER that is later replaced by the value.

var myObj = {
  color: 'red',
  doSomething: function (arg) {
  alert('Do someting called with ' + arg);
  }
}

var placeholder = '____PLACEHOLDER____';
var fns = [];
var json = JSON.stringify(myObj, function(key, value) {
  if (typeof value === 'function') {
    fns.push(value);
    return placeholder;
  }
  return value;
}, 2);

json = json.replace(new RegExp('"' + placeholder + '"', 'g'), function(_) {
  return fns.shift();
});

console.log(json)

https://gist.github.com/cowboy/3749767