<form>
<input type="text" id="name" name="name" placeholder="Имя" required="">
<input id="order" name="type" onclick="add()" type="button" value="Заказать">
<input type="checkbox" name="price" value="1">
<input type="checkbox" name="price" value="2">
<input type="checkbox" name="price" value="3">
<input type="checkbox" name="price" value="4">
<input type="checkbox" name="price" value="5">
</form>
<script>
function add(){
var a = "";
var elems = document.getElementsByName("price");
for(var i =0; i<elems.length; i++){
if(elems[i].checked) a += elems[i].value;
}
document.getElementById("name").value = a;
}
</script>