Assembling a var in Javascript

Question

This is looping in a timeout function. The nw remains undefined or is reset to undefined again at each new start. Why is that?

$("#wert"+i).load('variable.html #w'+i);
if(! nw){
alert(nw);
var nw = eval('neuerwert'+i); // Here I set the var nw, so why is it undefined again the next time around?
}
if ($("#w"+i).html() != nw){
wertaenderung('#wert'+i);
nw = $("#w"+i).html();
};

You need to put the variable declaration outside the function so it persists. — Barmar, Jul 24 '13 at 12:00
That's an answer (indeed, the correct one), more than a comment. — Mitya, Jul 24 '13 at 12:02
shouldn't all that code be in a callback function triggered by `.load` ? — Alnitak, Jul 24 '13 at 12:10

Philipp Sander · Accepted Answer · 2013-07-24T12:08:52.160

1

the variable nw has to be in the right scope:

var nw;
$("#wert"+i).load('variable.html #w'+i);
if(! nw){
    alert(nw);
    nw = eval('neuerwert'+i);
}
if ($("#w"+i).html() != nw){
    wertaenderung('#wert'+i);
    nw = $("#w"+i).html();
};

you USED the variable before you DECLARED it

edited Jul 24 '13 at 12:08

answered Jul 24 '13 at 12:00

Philipp Sander

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3

is the OP supposed to play "spot the difference" ? – Alnitak Jul 24 '13 at 12:01
1

Javascript variables are not confined to if-statements. See function four in http://stackoverflow.com/questions/500431/javascript-variable-scope – user694844 Jul 24 '13 at 12:07
Well, that makes sense but I want it to be undefined the first time around and not defined. – Coffeehouse Jul 24 '13 at 12:08

Zaheer Ahmed · Answer 2 · 2013-07-24T12:12:08.897

1

try moving nw out of load function:

var nw;
$("#wert" + i).load('variable.html #w' + i);
if (!nw) {
    alert(nw);
    nw = eval('neuerwert' + i);
}
if ($("#w" + i).html() != nw) {
    wertaenderung('#wert' + i);
    nw = $("#w" + i).html();
};

edited Jul 24 '13 at 12:12

answered Jul 24 '13 at 12:01

Zaheer Ahmed

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it's not really global – Philipp Sander Jul 24 '13 at 12:04

Damien · Answer 3 · 2013-07-24T12:05:34.470

1

Just remove the "var" in this line :

var nw = eval('neuerwert'+i);

So you will initialize the nw variable in the global context.

By writing var nw = ... you create a local variable that is removed when you leave the callback function.

edited Jul 24 '13 at 12:05

answered Jul 24 '13 at 12:04

Damien

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Assembling a var in Javascript

3 Answers3