It could be because you're trying to react to events on an html element that isn't clickable. This tutorial will explain how
Making Elements Clickable
Because of the way Safari on iOS creates events to emulate a mouse, some of your elements may not behave as expected on iOS. In particular, some menus that only use mousemove handlers, as in Listing 6-1, need to be changed because iOS doesn’t recognize them as clickable elements.
Listing 6-1 A menu using a mouseover handler
<span onmouseover = "..."
onmouseout = "..."
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</span>
To fix this, add a dummy onclick handler, onclick = "void(0)"
, so that Safari on iOS recognizes the span element as a clickable element, as shown in Listing 6-2.
Listing 6-2 Adding an onclick handler
<span onmouseover = "..."
onmouseout = "..."
onclick = "void(0)">
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</span>