In this example we use the dom to access elements, and then use the eval function to evaluate a user-entered formula
Simply type in a string such as 32 + 98 * 6
and click GO.
COMPUTE :
<script>
var answer;
function init(){
answer=document.getElementById("ans").firstChild;
}
function comp(id){
var res;
var el = document.getElementById(id);
try {
if ( el.value != "" ){
res = eval(el.value);
answer.data = res;
}
}catch (e) {
alert("Cannot evaluate " + el.value);
el.focus();
return;
}
}
</script>
And the answer is: 48