 | View Full Version : help with some simple javascript on select code housefire 02-07-2008, 11:51 PM So ive got a drop down select menu with options 1 - 10. (i.e. "1" "2" "3" etc..) When the user selects 3 from the select box, i need to do a math equation of 3 x 10 and put the result of 30 into a text field. Anyone got a function that might help? Kohrar 02-08-2008, 12:28 AM Try: <head> <title>Javascript Demo</title> </head> <body> <script> function updateValue() { document.getElementById('Return').innerHTML = document.getElementById('selectField').value * 10; document.getElementById('ReturnText').value = document.getElementById('selectField').value * 10; } </script> <form> <select name="test" id="selectField" onChange="updateValue();"> <option value="1">1</option> <option value="2">2</option> <option value="3">3</option> <option value="4">4</option> </select> <br /> <!-- Text inside <span> --> <span id="Return"></span> <br /> <!-- Or, just form input box --> <input type="text" id="ReturnText" value="" /> </form> </body> </html> This will just update the value on both the textbox and on the page. If you need any explaination about the html/javascript, don't hesitate to ask :) housefire 02-08-2008, 01:42 AM that worked perfect, however now im trying to update a 3rd text box with the sum of the first one. the code now is document.getElementById('subtotal').value = (document.getElementById('attendee_total').value + document.getElementById('total_dinner').value); but instead of adding 100 + 50 as 150, its outputting 10050 as the result. Ideas? Kohrar 02-08-2008, 01:57 AM Looks like it's concatenating the two values, maybe because it's reading it as a string... I guess you can try parseInt(), or parseFloat() for decimals. document.getElementById('subtotal').value = parseInt(document.getElementById('attendee_total').value) + parseInt(document.getElementById('total_dinner').value); joeshacks 02-08-2008, 01:59 AM that worked perfect, however now im trying to update a 3rd text box with the sum of the first one. the code now is document.getElementById('subtotal').value = (document.getElementById('attendee_total').value + document.getElementById('total_dinner').value); but instead of adding 100 + 50 as 150, its outputting 10050 as the result. Ideas? thats because javascript thinks the values are strings, you need to convert them to integers or floats.. try something like.. document.getElementById('subtotal').value = eval((document.getElementById('attendee_total').value) + eval(document.getElementById('total_dinner').value)); housefire 02-08-2008, 02:33 AM thats because javascript thinks the values are strings, you need to convert them to integers or floats.. try something like.. document.getElementById('subtotal').value = eval((document.getElementById('attendee_total').value) + eval(document.getElementById('total_dinner').value)); try this but it didnt work. housefire 02-08-2008, 02:35 AM Looks like it's concatenating the two values, maybe because it's reading it as a string... I guess you can try parseInt(), or parseFloat() for decimals. document.getElementById('subtotal').value = parseInt(document.getElementById('attendee_total').value) + parseInt(document.getElementById('total_dinner').value); works perfect. thanks. Kohrar 02-08-2008, 02:37 AM Glad it worked! Good luck with your project :) |