Jquery keypress event ignore arrow keys

I would also submit that you should be ignoring other keys that should not directly result in a new query. Keys like shift, scroll-lock, and end, for example. After consulting the same keycode list that @theyetiman linked to, I came up with this if statement to ignore all keys that shouldn't matter (note the swap of keypress for keyup to allow capture of important keys like backspace):

$('.search-terms').on('keyup', function(ev) {
    if ((ev.keyCode > = 9 && ev.keyCode <= 45) || (ev.keyCode >= 91 || ev.keyCode <= 93) || (ev.keyCode >= 112 || ev.keyCode <= 145)) {
        return;
    }
});

You need to filter out the arrow key codes (37,38,39,40), try this:

Note the function(e) in place of function() - this allows you to grab the event and therefore the key code.

$('#search-form .search-terms').on('keydown', function(e){
    // get keycode of current keypress event
    var code = (e.keyCode || e.which);

    // do nothing if it's an arrow key
    if(code == 37 || code == 38 || code == 39 || code == 40) {
        return;
    }

    // do normal behaviour for any other key
    $('#search-items #autocom').fadeIn();
});

Click for a list of key codes

A note from the docs on keypress/keyup/keydown:

Note that keydown and keyup provide a code indicating which key is pressed, while keypress indicates which character was entered. For example, a lowercase "a" will be reported as 65 by keydown and keyup, but as 97 by keypress. An uppercase "A" is reported as 65 by all events. Because of this distinction, when catching special keystrokes such as arrow keys, .keydown() or .keyup() is a better choice.

The keypress event works in almost all situations but it's prudent to use keyup or keydown because some browsers (I think some older version of Firefox) don't detect certain keys, such as arrow keys, using the keypress event.