how to pass checkbox value to javascript function

Question

my code is :

<input type="checkbox" name="area" id="area" value="0">Some Text1</input>
<input type="checkbox" name="area" id="area" value="80">Some Text2</input>

and javascript code is

function calc(){var textValue1 = document.getElementById('quantity').value;
var textValue2 = document.getElementById('area').value;
document.getElementById('cost').value = textValue1 * textValue2 ; }

but it isn't working.

Answer 1

Try this:

valueChange = function(item){
	alert(item.value);
}

<form name="form1" method="post" action=" insert_data.php">
    Delivery Location
    <input onChange="valueChange(this)" type="checkbox" name="area" id="area" value="0">Inside city </input>
    <input onChange="valueChange(this)" type="checkbox" name="area" id="area" value="80">Outside city </input>
    </form>