ни хрена не понятно, что хотите, так чтоли?
<body>
<input type = "text" id = "first"></input>
<input type = "text" id = "second"></input>
<input type = "text" id = "third"></input>
<button id = "getFromInput">get values</button>
<script type = "text/javascript">
var items = ['значение1', 'значение2', 'значение3'];
//inputs
var first = document.getElementById("first");
var second = document.getElementById("second");
var third = document.getElementById("third");
//button
var getFromInput = document.getElementById("getFromInput");
getFromInput.onclick = function() {
items[0] = first.value;
items[1] = second.value;
items[2] = third.value;
alert(items);
}
</script>
</body>