JAVASCRIPT - Uncaught TypeError: Cannot read property 'value' of null
Question
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Javascript Form Testing</title>
</head>
<body>
Name: <input type="text" name="Name" value="Name" id="fname"> <br>
Email: <input type="text" name="Email" value="Email" id="mail" > <br>
Phone: <input type="text" name="Number" value="Phone Number" id="dvr" onchange="validatePhone();">
<span id="phoneval"> ?</span>
<script type="text/javascript">
phonenum = document.getElementById("dvr").value.length;
function validatePhone() {
if (phonenum == 10){
document.getElementById('phoneval').innerhtml="<-- Valid";
}
else{
document.getElementById('phoneval').innerhtml="<-- Not Valid";
}
}
</script>
</body>
</html>
Hi, I was getting the error 'Uncaught TypeError: Cannot read property 'value' of null' when the tag was in the head, but since I moved it, it went away. However, now it outputs no error and does NOTHING. Please help?
Sorry for any formatting and things, new :/
2 answers
solution1
4 ACCPTED 2012-08-13 04:33:36
Edit:
Slightly different implementation that works: http://jsfiddle.net/SfTR2/ Make sure the JS is loaded after the HTML, or use window.onload
Original answer:
You need to get the length within the validation function:
function validatePhone() {
var phonenum = document.getElementById("dvr").value.length; //MOVE IT HERE
if (phonenum == 10){
document.getElementById('phoneval').innerHTML="<-- Valid";
}
else{
document.getElementById('phoneval').innerHTML="<-- Not Valid";
}
}
As previously you were caching the empty length.
Also, as @su mentioned, you need to use innerHTML
solution2
0 2012-08-13 04:32:26
add
validatePhone();
to the end of the script (you defined the function but never called it). And change innerhtml to innerHTML
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