Problem with variable scope in javascript

Question

Ok I am definitely puzzled, why this is not returning 6 in textarea. It doesn't return anything. I figured that it has something to do with js scopes, but i cant figure it out.

<body>

    <script language="Javascript">
    var broj = 5;  

    function Inci(){
    var broj++;
    document.frmMain.VrsteHolder.value = broj;
    }

    </script>

    <form name="frmMain" method="get" action="script.php">

    <textarea name="VrsteHolder" rows="4"> </textarea>
    <input type="button" value="Dodaj porudzbinu" name="buttonDodaj" onClick="Inci();"/> 

    </form>

</body>

The correct answer is already given, but if you wish to learn more about js scoping, read this: adequatelygood.com/2010/2/JavaScript-Scoping-and-Hoisting — Martin Jespersen
– Martin Jespersen, Commented Feb 8, 2011 at 23:24

Jacob Relkin · Accepted Answer · 2011-02-08 23:02:07Z

3

Get rid of the var keyword inside of the Inci function.

var redeclares variables in the current scope, so it will redeclare broj every invocation of Inci.

This would be the correct way:

var broj = 5;  

function Inci(){
   document.frmMain.VrsteHolder.value = ++broj;
}

answered Feb 8, 2011 at 23:02

Jacob Relkin

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3 Comments

JCOC611 Over a year ago

+1 usually one uses the var inside a function for the sake of leaving the outside variables untouched (ex. you have var hey outside and need to use the same name in the function without editing the global one)

Dejan Stuparic Over a year ago

ok i did that, but now result in textarea is NaN. Not number 6 as i expected.

Dejan Stuparic Over a year ago

I figure that is right solution, but for me it keep returning NaN. I will try to rework rest of code, thx anyway.

Cfreak · Accepted Answer · 2011-02-08 23:02:53Z

0

because the var keyword defines the variable. Remove var from your function:

function Inci(){
    broj++;
    document.frmMain.VrsteHolder.value = broj;
    }

answered Feb 8, 2011 at 23:02

Cfreak

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1 Comment

Dejan Stuparic Over a year ago

ok i did that, but now result in textarea is NaN. Not number 6 as i expected.

Nick Craver · Accepted Answer · 2011-02-08 23:04:32Z

0

The problem is var as the other answers detail, redeclaring your variable, or attempting to rather, and actually throwing a syntax error because of the combination.

As an aside though that I'm seeing less: don't forget you can increment and get the result immediately by having the ++ (increment operator) before the variable, for example:

function Inci(){
  document.frmMain.VrsteHolder.value = ++broj;
}

You can test that version out here.

answered Feb 8, 2011 at 23:04

Nick Craver

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1 Comment

Dejan Stuparic Over a year ago

ok i did that, but now result in textarea is NaN. Not number 6 as i expected.

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