Еще вариант
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<script>
$(function () {
var a = {};
$("form").serializeArray().map(function (x) { a[x.name] = x.value; });
alert(JSON.stringify(a))
});
</script>
</head>
<body>
<form>
<input type="text" class="function1" name="Диаметр" value="1">
<input type="text" class="function2" name="Масса" value="2">
<input type="text" class="function3" name="Размер" value="3">
<input type="text" class="function4" name="Материал" value="4">
<input type="text" class="function5" name="Цвет" value="5">
</form>
</body>
</html>