View Full Version : Need Help on Javascript Calculator

Jan 22nd, 2012, 04:34 PM
Hi all master and expert coders

I am working on a calculator which using the instructor's codes from the school. The problem that I having right now is the operator. I have successfully complete only the addition, but could not manage on subtraction and the rest operator. I hope experienced codes would help me out on this. Below is my codes.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<script type="text/javascript">
function calculate() {
var value1 = parseInt(validate(document.getElementById("value1").value));
var value2 = parseInt(validate(document.getElementById("value2").value));
document.getElementById("result").value = addition(value1, value2);
document.getElementById("result").value = subtraction(value1, value2);
document.getElementById("result").value = multiplication(value1, value2);
document.getElementById("result").value = division(value1, value2);

function validate(value) {
if (value == null || value == "") {
alert("Required Field");
return 0;
} else if (isNaN(value)) {
alert("Must be a number");
return 0;
else return value;

function addition(value1, value2){
return value1 + value2;
// trying to use the same addition return statement but fail.
function radioButtonCheck() {
if ((document.getElementById("radio1").checked == false)
&& (document.getElemtById("radio2").checked == false)) {
alert("Please select a radio button");
valid = false;
function checkboxCheck() {
if ((document.getElementById("cbox1").checked == false)
&& (document.getElementById("cbox2").checked == false)) {
alert("Please select a checkbox");
valid = false;
function dropDownListCheck() {
if ((document.getElementById("ddlOperator").selectedIndex == 0)) {
alert("Please select a operator");
valid = false;


<title>Calculator By Alsus</title>
<table border = "1">
<td>Value 1:</td>
<td><input type="text" id="value1" name="value1" /></td>
<td>Value 2:</td>
<td><input type="text" id="value2" name="value2" /></td>
<td><input type="text" id="Operator" name="Operator" /></td>
<td><input type="radio" id="radio1" name="radio1" value="radio1" />Radio1<br /></td>
<td><input type="radio" id="radio2" name="radio2" value="radio2" />Radio2<br /></td>
<td><input type="checkbox" id="cbox1" name="cbox1" value="cbox1" />Checkbox 1<br /></td>
<td><input type="checkbox" id="cbox2" name="cbox2" value="cbox2" />Checkbox 2<br /></td>
<select id="ddlSelect">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
<td><input type="text" id="result" name="result" /></td>
<input type="submit" id="btn_sub" name="btn_sub" value="Submit" onclick="calculate()" />
<input type="reset" id="btn_res" name="btn_res" value="Reset" />

Philip M
Jan 22nd, 2012, 05:40 PM
I don't understand what the radio buttons and checkboxes are supposed to do. In any case you simply test whether or not one of them has been selected, and do not capture the value. Same with the select list. You should include an initial option "Choose an operator" and then capture the selected value onchange.

valid = false does nothing as it is not referenced anywhere else.

To validate the inputs use var val1 = Number(document.getElementById("value1").value) || 0;
That is, if the entry returns NaN change it to the number 0.

Avoid using the same name (value1) for an HTML form element and a Javascript variable. It is very dangerous!

Typos such as getElemtById will cause your script to fail.

You are not submitting a form so your submit button should be a plain button.

Surely what you are trying to do is simply evaluate value1 operator (+-*/) value2 where the operator is the chosen value of the select list. It does not need a separate function for each operator. Be careful not to divide by zero!

BTW, when posting here please help us to help you by following the posting guidelines and wrapping your code in CODE tags. This means use the octothorpe or # button on the toolbar. You can (and should) edit your previous post.

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