function Player(name)
    {            
        this._name = name;                     
        this._id = "Player"+(Player_ID++);
    };

var newPlayer = new Player(newUnitName);
alert(JSON.stringify(newPlayer));

What I want to do is stop displaying the id value. Is there a way to make the id variable tranient. Please help

function Player(name)
    {            
        this._name = name;                     
        this._id = "Player"+(Player_ID++);
    };

var newPlayer = new Player(newUnitName);
alert(JSON.stringify(newPlayer));

What I want to do is stop displaying the id value. Is there a way to make the id variable tranient. Please help

• javascript
• oop

• 2 Possible duplicate of json stringify : How to exclude certain fields from the json string – James Thorpe Commented Apr 28, 2016 at 7:34

3 Answers 3

Every object has a method toJSON(), which is invoked when the object should be serialize using JSON.stringify().

From MDN article on JSON.stringify():

If an object being stringified has a property named toJSON whose value is a function, then the toJSON() method customizes JSON stringification behavior: instead of the object being serialized, the value returned by the toJSON() method when called will be serialized

The following example creates a different serialization function, which will exclude the _id:

var Player_ID = 0;
function Player(name) {            
 this._name = name;                     
 this._id = "Player"+(Player_ID++);
 this.toJSON = function() {
   return {
     _name: this._name
   };
 };
};

var newPlayer = new Player('Name 1');
console.log(JSON.stringify(newPlayer)); // prints {"_name": 'Name 1'}

Check the working demo.

If you don't need to enumerate over this property you can use non-enumerable properties:

    function Player(name)
        {            
            this._name = name;                     
            Object.defineProperty(this, '_id', {
              enumerable: false
            });
        };

    var newUnitName = "Foo";
    var newPlayer = new Player(newUnitName);
    alert(JSON.stringify(newPlayer));

Targeting ES2022, you can achieve transient variables at least in 2 ways:

1. Using a private variable
2. Using an "accessor" variable

"use strict";
class Example {
    constructor() {
        this.#aTransientValue_accessor_storage = "transient";
        this.aNormalValue = "public";
        this.#aPrivateValue = "public";
    }
    #aTransientValue_accessor_storage;
    get aTransientValue() { return this.#aTransientValue_accessor_storage; }
    set aTransientValue(value) { this.#aTransientValue_accessor_storage = value; }
    #aPrivateValue;
}
const example = new Example();
console.log(example); /// prints { "aNormalValue": "public" }

Typescript even introduced the "accessor" keyword, which can be used for this purpose.

Here is the TS equivalent code:

class Example {
    accessor aTransientValue = "transient";
    public aNormalValue = "public"
    #aPrivateValue = "public"
}

const example = new Example();

console.log(example);