Getting strange behavior when doing if(1>0) in JavaScript

Question

I'm really at a loss here. I have the following code:

function AddHeightToBottom(footerHeight)
{
    if ($('#myId1').length)
    {
        $('#myId1').height($('#myId1').height() + footerHeight);
    }
    console.log(('#myId2').length);
    if ($('#myId2').length > 0)
    {
        var dHeight = $('#myId1').height();
        var aHeight = $('.AF').height();
        $('#myId1').height(dHeight + aHeight);
        var newHeight = $('#myId1').height();
        alert(newHeight);
    }
    else
    {
        alert('why?!??????');
    }
}

$('#myId2').length is coming out to 1, as I'd expect. However, when it does the comparison

if(1 > 0)

it's doing thing 2 EVERY time and I have no idea why. Any help would be appreciated.

It seems to work as expected. Can you create an example that exhibits this behavior? — Mike Cluck
– Mike Cluck, Commented May 19, 2016 at 20:52
You are using jquery, so make sure you are running it in document.ready: $( document ).ready(function() { if($('#element').length > 0) { //do thing 1 } else { //do thing 2 } }); — Dan Weber
– Dan Weber, Commented May 19, 2016 at 20:55
The code shown works as expected, which means there is something about the rest of the code that isn't working as you expect it to do. You need to post enough of your code to enable us to help you, but the if/else is not, itself, broken or misbehaving. — David Thomas
– David Thomas, Commented May 19, 2016 at 20:57
@SeanSmyth Look. You need to give us code that we can verify fails. The code you have posted is not enough to recreate the bug. We need enough to recreate the bug. If we cannot recreate the bug then we cannot confirm why it's failing for you. — Mike Cluck
– Mike Cluck, Commented May 19, 2016 at 20:59

Dan Weber · Accepted Answer · 2016-05-20 00:33:41Z

5

You are using jquery, so make sure you are running it in document.ready:

$( document ).ready(function() { 
   if($('#element').length > 0) { //do thing 1 } 
   else { //do thing 2 } 
});

If you are calling this in another function, then that function must appear in document.ready. A page can't be manipulated safely until the document is "ready." jQuery detects this state of readiness for you. Code included inside $( document ).ready() will only run once the page Document Object Model (DOM) is ready for JavaScript code to execute. Code included inside $( window ).load(function() { ... }) will run once the entire page (images or iframes), not just the DOM, is ready. * Quoted from link below.

https://learn.jquery.com/using-jquery-core/document-ready/

function AddHeightToBottom(footerHeight)
{
    if ($('#myId1').length){
        $('#myId1').height($('#myId1').height() + footerHeight);
    }
    console.log(('#myId2').length);
  
    if ($('#myId2').length > 0)
    {
        alert("See, it works...");
      
        var dHeight = $('#myId1').height();
        var aHeight = $('.AF').height();
        $('#myId1').height(dHeight + aHeight);
        var newHeight = $('#myId1').height();
        alert("New height: " + newHeight);
    }
    else
    {
        alert('why?!??????');
    }
}

$( document ).ready(function() { 
  var footerHeight = 25;
  AddHeightToBottom(footerHeight);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<div id="myId1">div with id of myId1</div>
<br>
<div id="myId2">div with id of myId2</div>

edited May 20, 2016 at 0:33

answered May 19, 2016 at 20:58

Dan Weber

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2 Comments

Dan Weber Over a year ago

Edited response to show it working. Perhaps you forgot to load jQuery? Are you including it twice? It's something related to jQuery in my opinion.

Dan Weber Over a year ago

Try document.getElementById("myId2").length if you want to confirm it's related to your jquery setup.

Sean Smyth · Accepted Answer · 2016-05-20 15:51:25Z

0

The element I was trying to grab was being loaded in an iFrame, so document.ready() wasn't catching it. I don't know why Firebug was telling me the length was 1 when it was actually 0.

answered May 20, 2016 at 15:51

Sean Smyth

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