Update another property, when a property changes?

Question

I want to create a dependent property on my javascript object. I have an object like in the code snippet. I want to update isPawn property; when isNew property changes.

Is there a way for do something similar that automatically;

if(isNew){
   isPawn = true;
}

But they are not have to be same. isNew can be 'false', when isPawn is 'true'

My Object:

var Soldier = function (id,name) {
    this.id = id;
    this.name = name;
    this.isPawn = false;
    this.isNew = false;
}

Answer 1

Yes, you can do this using a setter, here is an example:

 class Soldier { #isNew = false; constructor(id,name) { this.id = id; this.name = name; this.isPawn = false; } set isNew(val) { this.#isNew = val; this.isPawn = val; } get isNew() { return this.#isNew; } } const soldier = new Soldier(); soldier.isNew = true; console.log('isNew:', soldier.isNew, 'isPawn', soldier.isPawn); soldier.isNew = false; console.log('isNew:', soldier.isNew, 'isPawn', soldier.isPawn); soldier.isPawn = true; console.log('isNew:', soldier.isNew, 'isPawn', soldier.isPawn);

#isNew is a private field in this case I'm using it to keep track of what the value of isNew should be (what the getter should return).

Here is an example using a function instead of a class:

 var Soldier = function(id, name) { this.id = id; this.name = name; this.isPawn = false; this.isNewPriv = false; Object.defineProperty(this, 'isNew', { set: function(val) { this.isNewPriv = val; this.isPawn = val; }, get: function() { return this.isNewPriv } }); } var soldier = new Soldier(1, 'none'); soldier.isNew = true; console.log("isNew:", soldier.isNew, "isPawn:", soldier.isPawn); soldier.isNew = false; console.log("isNew:", soldier.isNew, "isPawn:", soldier.isPawn); soldier.isPawn = true; console.log("isNew:", soldier.isNew, "isPawn:", soldier.isPawn);

Answer 2

Make a class and instantiate as needed

 class Soldier { constructor(id, name, isNew) { this.id = id; this.name = name; this.isPawn = isNew? true: {something: "whaterverElse"}; this.isNew = isNew; } DoSomething(){ this.isNew = false; } } var soldier = new Soldier(1, 'Tim', true); console.log(soldier); function somethingElseHappened(){ soldier.DoSomething(); } somethingElseHappened(); console.log(soldier);

Answer 3

you can make a default values for this properties like this:

var Soldier = function (id,name,isPawn = false,isNew = false) {
    this.id = id;
    this.name = name;
    this.isPawn = isPawn;
    this.isNew = isNew;
}

and if you want to change there values to any object for you just do like this:

var newSolider = new Solider(1,"foo",false,true);