Using Javascript to compare two input numbers in HTML?
Question
I am using Notepad++ to create a simple web page where a user types in two numbers into a text box, and then presses a button. When they press the button something comes up that tells them whether the first or second number is greater. I have the following code but cant get anything to come up. Does anyone know whats wrong?
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8" />
<title>Assignment 10 Form</title>
<script type="text/javascript">
function greaterNum(){
var value1;
var value2;
value1 = document.First_num.value;
value2 = document.last_num.value;
if (value1 > value2){
alert('Value 1 is greater than value 2');
document.body.style.background = "orange";
}
}
</script>
<style type="text/css">
body{background-color: #40FF00;
margin-left: auto;
margin-right: auto;
width: 60%;
}
#container{
border: 2px solid yellow;
padding: 20px;
}
</style>
</head>
<body>
<h1>Assignment 10</h1>
<div id="container">
<div class="Num">
<form>
<label class="label1">Enter Value 1:</label>
<input type="text" name="First_num" value=" " />
<label class="label1">Enter Value 2:</label>
<input type="text" name="last_num" value=" " />
<br/>
<input type="button" value=" Which number is greater? " onclick="greaterNum();" />
</form>
</body>
</html>
4 answers
solution1
5 2013-04-09 23:47:46
Values from inputs are retrieved as strings, you need to convert it to number. Try this:
value1 = +document.First_num.value;
value2 = +document.last_num.value;
Also, try to be consistent when naming your input, why caps for one and lowercase for the other?
solution2
0 2013-04-09 23:50:45
You may need to use:
value1 = document.getElementById("First_num").value;
However, this only works if you assign the elements id attributes:
<input type="text" id="First_num" name="First_num" value=" " />
Otherwise, use the getElementsByName .
Hope this helps!!
solution3
0 2013-04-10 02:29:54
Convert to floats.
value1 = parseFloat(document.First_num.value);
value2 = parseFloat(document.last_num.value);
solution4
-1 2013-04-09 23:48:59
Html is a string, not a value. You need to parse it in someway.
EDIT:
The problem seems to be grabbing the values, change it to getElementById and it works fine:
HTML
<h1>Assignment 10</h1>
<div id="container">
<div class="Num">
<form>
<label class="label1">Enter Value 1:</label>
<input type="text" id="First_num" name="First_num" />
<label class="label1">Enter Value 2:</label>
<input type="text" id="last_num" name="last_num" />
<br/>
<input type="button" id="clickme" value="Which number is greater?" onclick="greaterNum()" />
</form>
js
function greaterNum(){
var value1;
var value2;
value1 = document.getElementById("First_num").value;
value2 = document.getElementById("last_num").value;
if (value1 > value2){
alert(value1 - value2);
document.body.style.background = "orange";
}
}
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