Change value of passed variable in Javascript without return?

Question

I have the function change(x) which takes an integer and changes its value

function change(x) {
   x=26;
}

Then I make a variable and I try to change its value

window.onload=function(){
   var a = 10;
   change(a);
   console.log(a);
}

a doesn't change as I would expect. Is it possible to achieve this behaviour in JavaScript in a simple way without using return? I would prefer to avoid objects and globals.

Here is my whole code:

<!DOCTYPE html>
<html>
<head>
</head>
<body>
   <script>
   function change(x) {
      x=26;
   }
   window.onload=function(){
      var a = 10;
      change(a);
      console.log(a);
   }
   </script>
</body>
</html>

Yes, a = change(a);

JJJ
– JJJ

2013-03-31 11:33:40 +00:00
Commented Mar 31, 2013 at 11:33 — JJJ
– JJJ, Commented Mar 31, 2013 at 11:33
Check this answer: stackoverflow.com/questions/518000/…

NilsH
– NilsH

2013-03-31 11:34:53 +00:00
Commented Mar 31, 2013 at 11:34 — NilsH
– NilsH, Commented Mar 31, 2013 at 11:34

alex · Accepted Answer · 2013-03-31 11:34:07Z

3

JavaScript always passes arguments by value, so you can't do it as you originally written.

However, an object's value is a reference, so you could use an object.

However, that would be confusing for this use case. You should have that function return the transformed number.

answered Mar 31, 2013 at 11:34

alex

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3 Comments

Pithikos Over a year ago

The problem is that there is a callback function inside my "change" function, thus I cannot return the value. I get 'undefined' then.

dfsq Over a year ago

@Pithikos You should use callback function.

newacct Over a year ago

"However, an object's value is a reference" You mean, a variable's value is a reference, which points to an object.

Linus Kleen · Accepted Answer · 2013-03-31 11:34:34Z

1

You cannot pass a variable by reference like that (or at all). What you can do is pass an object and modify its properties:

function change(obj) {
    obj.a = 4;
}

var obj = {a: 0};
change(obj);

// obj.a is "4" now

answered Mar 31, 2013 at 11:34

Linus Kleen

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Comments

phiri861 · Accepted Answer · 2013-03-31 11:42:36Z

-2

I did this and it worked:

function change(x) {   
  x=26;  
  return x;  
}  
  window.onload=function(){  
  var a = 10;  
  console.log(change(a));  
}

Hope it helps

answered Mar 31, 2013 at 11:42

phiri861

52 bronze badges

1 Comment

Erik Escobedo Over a year ago

Adding a console.log(a) at the end of your window.onload function proves you wrong.

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