getElementById() inside For loop isnt working

Question

i have a form which have 39 text input fields. their ids are input1, input2 ... input39. what i want to do is if any of them doesnt contain any value then my script will delete it which is no problem. the problem is when i check the values of those text fields one by one it works fine but when i use a loop it shows error.so i ran a very simple test in the firebug console..

var i=1;
var asd="";

asd='input' + i;
var test=document.getElementById(asd).value;
asd="";
test;

if i run the above code in the firebug console then it works fine, shows the value of 1st textbox. but..

var i=1;
var asd="";

for(i=1;i<39;i++)
{
    asd='input' + i;
    var test=document.getElementById(asd).value;
    asd="";
    test;
}

if i run this code then i get TypeError: document.getElementById(...) is null

any idea why is this happening?? all the textboxes default value is "" (empty string)..

You sure you actually have 39 of them, all named correctly and without typos? Can you show us the exact error message? — user2357112, Dec 30 '13 at 15:10
`test;` ??? what do you want it to do? call the value? also, getElementById can return NULL, so its best to not call on it `.value` immediately. You sure you have 39 inputs with the name input1...input39? — Noam Rathaus, Dec 30 '13 at 15:10
are you sure there are ids at your dom from input1 to input38 — semirturgay, Dec 30 '13 at 15:10
Add a `console.log(i)` as the first line inside the loop, or `console.log(test)` after the problem line, so that you can see how far it gets before failing. Also, if you have 39 inputs your loop condition needs to be `i <= 39` (use `<=` rather than `<`), and there's no point setting `asd=""` at the end of each loop iteration. — nnnnnn, Dec 30 '13 at 15:10
Recreated your question in JsFiddle http://jsfiddle.net/XEU5b/ however it seems to be working fine — Rick Hoving, Dec 30 '13 at 15:12
http://stackoverflow.com/questions/9899372/pure-javascript-equivalent-to-jquerys-ready-how-to-call-a-function-when-the — Andy, Dec 30 '13 at 15:12
@Rick as far as I know, jsfiddle automatically start script when dom is ready. — Andy, Dec 30 '13 at 15:13
thanks to nnnnnnn i used console.log(i) and i get the mistake.. — Wahid Masud, Dec 30 '13 at 15:47

score 1 · Accepted Answer · answered Dec 30 '13 at 23:49

Somewhere in your loop you are calling an ID that does not exist. Make sure your input IDs are what you think they are and make sure your loop ends at the appropriate time. For example if you have IDs to input38 make sure your loop doesn't go to input39. And make sure you have IDs for each iteration of the loop (ex. input1 - 38).

score -1 · Answer 2 · answered Dec 30 '13 at 15:12

-1

First of all you have to set the limit of the for loop to 40 or <= 39 to include the 39th element.

Try this:

for (var i=1;i<=39;i++) {
    var asd = 'input' + i;
    var test = document.getElementById(asd).value;
    test;
}

answered Dec 30 '13 at 15:12

thehand

1

1

That's true, but doesn't explain the error the OP is getting. – nnnnnn Dec 30 '13 at 15:15
1

May you post the html code you're using? The only explainable reason is that some of the input field has a wrong id – thehand Dec 30 '13 at 16:07

getElementById() inside For loop isnt working

2 Answers2