jQuery.inArray() not working as expected

Question

What am I doing wrong here? The idea is that I can separate the arrow key presses from anything else, but the every key press is firing the alert 'you pressed an arrow key'. Any help would be great!

jsFiddle here or:

<input id='foo'>

<script>

$('#foo').keyup(function (e) {
    var key = e.keyCode;
    if ($.inArray(key, [37, 38, 39, 40])) {
        alert('you pressed an arrow key');
    } else {
        alert("you didn't press an arrow key");
    }
});

</script>

.inArray() returns an index, not a bool. Make sure to read the doc prior. — Dom
– Dom, Commented Mar 25, 2013 at 20:42
possible duplicate of jQuery.inArray not behaving as expected — user400654
– user400654, Commented Mar 25, 2013 at 20:44

Justin Bicknell · Accepted Answer · 2013-03-25 20:41:44Z

39

You have to check if it returns an index > -1. The index is -1 if there is no occurrence of the key in the array:

if ($.inArray(key, [37, 38, 39, 40]) >  -1)

answered Mar 25, 2013 at 20:41

Justin Bicknell

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3 Comments

MFB Over a year ago

But I want to check if the key IS in the array. Is that possible, or do I just reverse the logic of the function?

Justin Bicknell Over a year ago

if the index returned by that function is > -1 than that means the key IS in the array. In other words, the above will return true if it is in the array.

ucMax Over a year ago

Thanks, My mistake is that I think it returns a boolean value

Andy Meyers · Accepted Answer · 2013-03-25 20:46:43Z

3

The jQuery inArray function returns the index of the value. For the left arrow key (37) it is returning 0 and it is being interpreted as false. You should change your code to be >=0

   if ($.inArray(key, [37, 38, 39, 40]) > -1)

inArray

answered Mar 25, 2013 at 20:46

Andy Meyers

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Comments

user1980347 · Accepted Answer · 2013-03-25 20:48:07Z

3

The $.inArray method returns the index of the element if it is in the array, and if it is not in the array it returns -1, so you can't use it as an if condition. Change it to:

if($.inArray(key, [37, 38, 39, 40]) >= 0)) {

}

answered Mar 25, 2013 at 20:48

user1980347

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