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 = ""; 
 }

• Kos: Your identation doesn't really help with reading your code :).
• Jeroen: Have a look at this hoisting article, it may explain a few related concepts.
• Codebeat: better do: var dbaseterm = (dbasedata.indexOf("UK_CONTACTS") > -1)?'UK_CONTACTS':''
• user1106925: 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.

Answer 1

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;
}

Answer 2

Yes, you can do this and it is legal.

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

Answer 3

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.