ShiftKey not working on formsubmit

by David Refoua

HTML

<script>
function isPressed(e){
    alert(e.shiftKey);   //returns undefined instead of true|false  -_-
}
</script>

<form onsubmit="isPressed(event); return false;">
    <u>Hold shift down</u> and then
    <input type="submit" value="Click here to submit" />
</form>

<small>(This should <i>not</i> return <code>undefined</code>.)</small>

CSS

body{
    margin-top: 100px;
    background: #252525;
}
body, input{
    line-height: 15px;
    text-align: center;
    font-family: sans-serif;
    font-size: 11pt;
    font-weight: bold;
    color: white;
    text-shadow: 0 2px black;
    padding: 15px;
    vertical-align: middle;
}
input{
    -webkit-transition: .2s ease;
    -moz-transition: .2s ease;
    -ms-transition: .2s ease;
    -o-transition: .2s ease;
    transition: .2s ease;
    background: #125aed;
    outline: 0; margin: 0 20px;
    border: 2px solid black;
    border-radius: 4px;
    box-shadow: inset 0 1px rgba(255,255,255,.3), 0 2px 5px rgba(0,0,0,.3);
}
input:hover{
    background: #1233ef;
}
input:active{
    background: darkblue;
    box-shadow: 0 1px rgba(255,255,255,.3);
}
small{
    color: #ddd;
    margin-top: 50px;
    padding: 10px 0;
    display: block;
    font-weight: normal;
    background: #222;
    text-shadow: 0 1x black
}
/* I've designed this just for fun! ;) */