ansaurus

Question

Why does this code alert three undefined values?

Answer 1

+1 A:

Update:

Since you have just one input field, the below code will show just for that, that is button.

You could modify your function and it's call this way:

    <input type="button" value="Go" onclick="doIt()">

    function doIt(){
        var form = document.forms[0]; // get first form or adjust accordingly
        for (var i = 0; i < form.elements.length; i++){
            alert(form.elements[i].value);
        }
    }

Sarfraz 2010-07-26 18:30:40

"this" is the reference to the button, not the form.

HoLyVieR 2010-07-26 18:31:59

I am referencing the form object form the button. Is that whats making me get three undefined values? The undefined problem still exists even after trying your answer.

Babiker 2010-07-26 18:37:04

@Babiker: See my updated answer please.

Sarfraz 2010-07-26 18:39:01

@sAc i am still getting three undefined alerts.

Babiker 2010-07-26 18:42:09

It is on a button, it's just all on the same line.

jasongetsdown 2010-07-26 18:42:27

@jasongetsdown: Yes my answer is updated for that :)

Sarfraz 2010-07-26 18:44:15

@sAc , @jasongetsdown, @HolyVieR is anyone getting the alerts after running this code?

Babiker 2010-07-26 18:48:05

@Babiker: I have updated my answer with working demo, please check :)

Sarfraz 2010-07-26 18:53:58

Answer 2

+3 A:

You've having a problem because the array in form.elements isn't a true array. its a HTMLCollection which is an array-like object. As a result it isn't iterable with a for...in loop. Switch to a standard for loop and it works as expected.

The for...in loop is really meant for iterating through the properties of an object. It is not recommended for use on arrays (see the description section here).

jasongetsdown 2010-07-26 18:58:08

Answer 3

+2 A:

form.elements is an array-like structure which has three properties: length, item, namedItem. Hence with for-in loop, you are getting three alerts for each of these properties. A regular for loop would work correctly

Marimuthu Madasamy 2010-07-26 19:01:06

ansaurus

tags:

views:

answers:

Why does this code alert three undefined values?

related questions