Question

How I can sum up the values filled in unitprice array using javascript
Here is my html.

   <td>
       <input type="text" style="width: 60px; background: none repeat scroll 0% 0% rgb(255, 255, 255);" maxlength="4" id="unitprice" name="unitprice[]">
   </td>
   <td>
       <input type="text" style="width: 60px; background: none repeat scroll 0% 0% rgb(255, 255, 255);" maxlength="4" id="unitprice" name="unitprice[]">
   </td>

Answer 1

Change your HTML to use class instead of id (id must be unique):

<td>
    <input type="text" 
        style="width: 60px; background: none repeat scroll 0% 0% rgb(255, 255, 255);" maxlength="4" 
        class="unitprice" name="unitprice[]">
</td>
<td>
    <input type="text" 
        style="width: 60px; background: none repeat scroll 0% 0% rgb(255, 255, 255);"
            maxlength="4" class="unitprice" name="unitprice[]">
</td>

Then you can total via JavaScript (using jQuery .each() function):

var totalUnitPrice = 0;

$('.unitprice').each(function(index) {
    totalUnitPrice += parseInt($(this).val()); // parse the value to an Integer (otherwise it'll be concatenated as string) or use parseFloat for decimals
  });