Javascript - check object defined

[ismailc]

Good day,

I thought i had this sorted but it does not seem to check if the object is undefined / not created.

I'm trying to check if object is undefined & i tried a few methos but no luck
with the "value;" it returns the alert no to say that it is define where it is not

Please help

      var a = document.getElementById('VE10110INTEFT').value;
      if (a === undefined)
      { alert("yes");} else { alert("no");}
 
var a = document.getElementById('VE10110INTEFT').value;
if (typeof(a) === undefined)
 
var a = document.getElementById('VE10110INTEFT');
if (typeof(a) == "undefined")
 
var a = document.getElementById('VE10110INTEFT');
if (a == "undefined")
 

[ismailc]

I got it going :)

      var a = document.getElementById('VE10110INTEFT');
 
      if (a != null)
      { 
        alert("yes");
      }
      else
      {
        alert("no");
      }
 

[Dormilich]

if an input is not filled, it returns "" (empty string).

[ismailc]

Hi,
Thanks my problem was that the object was not created or loaded due to some business rules on the page & therefore i would get error on if condition to check value

Regards

[Dormilich]

then do

var a = document.getElementById('VE10110INTEFT');
if (a === undefined) { /* … */ }

[ismailc]

Hi,

I got it going using "!= null"

I did try the below, but i would get the error on the first line when defining the var.

var a = document.getElementById('VE10110INTEFT');
if (a === undefined)

Would also not work.
if (document.getElementById('VE10110INTEFT') === undefined)

Thanks I'm okay on this topic :)
I appreciate your help & time

[gits]

yes ... i think this is correct ... document.getElementById('nodeId') returns null when the element is not found ... so the check for null is sufficient.

kind regards

[Dormilich]

yes ... i think this is correct ... document.getElementById('nodeId') returns null when the element is not found

just went to look it up (DOM level 2 Core) … it indeed returns null if the element doesn’t exist.

so you could also test (unless the DOM implementation is faulty)

var a = document.getElementById('VE10110INTEFT');
if (a === null) { /* … */ }