javascript re-define a variable

Question

I'm getting stuck somewhere (as newbies do). Is it ok to re-define a variable once it has been trimmed and tested for content?

    function setarea() {

        var dbasedata = document.forms[0]._dbase_name.value;
            dbasedata = dbasedata.toUpperCase();
            dbasedata = dbasedata.replace(/\s/g, "");
            dbasedata = dbasedata.remove("UK_CONTACTS", "");

        if (dbasedata != "") {
            _area.value = _dbase_name.value;
        } 

   else var dbasedata = document.forms[0]._dbase_name.value;
            dbasedata = dbasedata.toUpperCase();
            dbasedata = dbasedata.replace(/\s/g, "");

        if (dbasedata.indexOf("UK_CONTACTS")>-1 {
        var dbaseterm = "UK_CONTACTS";
   else var dbaseterm = "";     
            }

Your identation doesn't really help with reading your code :). — Kos
– Kos, Commented May 30, 2012 at 18:18
Have a look at this hoisting article, it may explain a few related concepts. — Jeroen
– Jeroen, Commented May 30, 2012 at 18:21
better do: var dbaseterm = (dbasedata.indexOf("UK_CONTACTS") > -1)?'UK_CONTACTS':''; — Codebeat
– Codebeat, Commented May 30, 2012 at 18:24
A little off topic, but I'd chain those first lines in the function. var dbasedata = document.forms[0]._dbase_name.value.toUpperCase().replace(/\s/g, "").remove("UK_CONTACTS", ""); I assume .remove() is being added to String.prototype. — user1106925
– user1106925, Commented May 30, 2012 at 18:30

ThiefMaster · Accepted Answer · 2012-05-30 18:20:37Z

4

It makes no sense to use var more than once for the same variable in the same scope. Since all var x; are hoisted to the top of the scope every additional var on that variable will be a no-op.

Assigning a new value is fine though - they are variables and not constants after all.

function x() {
    var x = 123;
    foo();
    x = 456;
    var y = 'hello';
    var x = 678;
}

is actually this internally:

function x() {
    var x, y; // both are === undefined
    x = 123;
    foo();
    x = 456;
    y = 'hello';
    x = 678;
}

answered May 30, 2012 at 18:20

ThiefMaster

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Comments

Wouter J · Accepted Answer · 2012-05-30 18:18:56Z

1

Yes, you can do this and it is legal.

answered May 30, 2012 at 18:18

Wouter J

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2 Comments

Codebeat Over a year ago

It is legal but the 'var' declaration is not needed after line: ' dbasedata = dbasedata.remove("UK_CONTACTS", "");'

labman Over a year ago

I want to test the string to see if it contains UK_CONTACTS. If it does I want it to do something. Then, I want to test the the same original string after removing UK_CONTACTS (and white spaces) to see if there is anything else in the string. Not sure how to do that without re-defining the string again.

JMC · Accepted Answer · 2012-05-30 18:23:35Z

0

It may 'work', but isn't recommended. You don't need to redeclare it.

Probably want to run your code through JSLint . There are a few tidyness/bracing issues you would want to address.

answered May 30, 2012 at 18:23

JMC

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