Convert object to JSON omitting certain (private) properties

Question

I\'ve been using dean edwards base.js (http://dean.edwards.name/weblog/2006/03/base/) to organise my program into objects ( base.js is amazing btw, if you havent used it before

Answer 1

You probably know that you cannot have private properties in JavaScript.

Interestingly, if you pass an object to JSON.stringify which has a method toJSON, JSON.stringify will automatically call that method to get a JSONable representation of that object. So all you have to do is implement this method.

For example you can create a shallow copy of the object which only contains the properties you want to copy:

MyConstructor.prototype.toJSON = function() {
    var copy = {},
        exclude = {ref: 1};
    for (var prop in this) {
        if (!exclude[prop]) {
            copy[prop] = this[prop];
        }
    }
    return copy;
};

DEMO

Another way would be to use a custom replacer function, but it might be more difficult to control which ref to exclude and which one to keep (if different objects have ref properties):

JSON.stringify(someInstance, function(key, value) {
     if(key !== 'ref') {
         return value;
     }
});

DEMO

Answer 2

here is sample to to set variable visibility

function Obj(){
       this.ref = 'public property'; // this property is public from within the object

       var ref = 'private proerty'; // this property is private.

       var self = this;

        this.showRef = function(){
            alert(ref);
            alert(self.ref);
        };
    }

var obj = new Obj();
obj.showRef();