Sylar V,
<!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 = ["Диаметр","Масса","Размер"].reduce(function(b, a, c) {
b[a] = document.querySelector(".function" + (c + 1)).value;
return b
}, {});
alert(JSON.stringify(a))
})
</script>
</head>
<body>
<input type="text" class="function1" value="1">
<input type="text" class="function2" value="2">
<input type="text" class="function3" value="3">
</body>
</html>