JavaScript passing argument via reference

Question

let say I've got this kind of code:

var obj1 = {test: false};
function testCondition(condition){
 if (!condition){
 testCondition(condition);
 }
}
testCondition(obj1.test);

above code will pass false as argument to testCondition. How can I do to pass reference to obj1.test instead of passing it's value?

EDIT wow, thanks for quick responses!! :) But I would like to add, that I cannot pass the whole object, because I would like to build one generic function/method which would just check parameter and do onComplete callback or onError callback. Above code is only example of situation where I am right now.

• Bergi: Why do you want to cause a recursion stack overflow?
• Bergi: What would you need the reference for? Do you intend to assign to the object property?
• Krystian: I'm developing JS application which has many async AJAX requests, by above function I would like to test if requests are finished (many parallel requests, and all kind of crazy crap. ;) ) And because of D.R.Y. I dont want to have multifunctions to check same thing, but in different conditions.
• Bergi: Well in async environments they tell you when they're finished via callbacks - no need to test for it. Or maybe you should post your actual code; this abstracted version doesn't demonstrate your problem.
• Krystian: no, i think it would be pointless. Anyway I think I get the picture. thanks!

Answer 1

You have two choices, from what I can see:

1. Pass the object itself, instead of its member. You can then access and modify the member:

   function testCondition(object) {
    if (!object.test) {
    testCondition(object);
    }
   }
   testCondition(obj1)
   

2. Alternatively, since you're changing a single value, you can have that value be returned by the function:

   function testCondition(condition) {
    if (!condition){
    return testCondition(condition);
    }
   }
   obj1.test = testCondition(obj1.test);
   

FYI, your code as you've displayed it right now will cause an infinite recursion if condition is false.

Answer 2

What's wrong with return values?

Alternatively you can wrap the argument in an object:

function foo(arg) {
 var val = arg.val;
 // do something with val
 arg.val = val;
}
var arg = {val:"bar"};
foo(arg);
// do something with arg.val

• David Foerster: Indeed. Fixed it just now.

Answer 3

You can't.

Pass obj1 instead, then examine condition.test inside the function.

Answer 4

You can't. JavaScript passes objects and arrays by reference, primitives (integers, strings, booleans) by value. What you're asking for is impossible, except by bad work-arounds:

function ugly(result) {
 result.success = true;
}
var result = {};
ugly(result);

Instead, just return your value. It's how JavaScript is meant to work.

Answer 5

pass the whole object instead of its property:

testCondition(obj1);

and then

if(!passedObj.test){

etc...