I'm new to Javascript and am learning the basics via a textbook that focuses on its applications in IE 7+ and Firefox 2+. However, I am using Chrome and am getting the following error when running the program given in the book: "blocked a frame of origin 'null' from accessing a cross-origin frame." Can anyone tell me what is causing the error and how I can fix it? The two programs are below.
//This is the program being loaded into the browser
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Example</title>
<script type="text/javascript">
function calcFactorial(factorialNumber){
var factorialResult = 1;
for(;factorialNumber>0;factorialNumber--) factorialResult *= factorialNumber;
return factorialResult;
}
</script>
</head>
<frameset cols="100%,*">
<frame name="fraCalcFactorial" src="calcfactorial.htm"/>
</frameset>
</html>
Below is the src file
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Example</title>
<script type="text/javascript">
function butCalculate_onclick(){
try{
if (window.top.calcFactorial == null)
throw "This page is not loaded within the correct frameset";
if (document.form1.txtNum1.value == "")
throw "!Please enter a value before you calculate its factorial";
if (isNaN(document.form1.txtNum1.value))
throw "!Please enter a valid number";
if (document.form1.txtNum1.value < 0)
throw "!Please enter a positive number";
}
catch(exception){
if (typeof(exception) == "string"){
if (exception.charAt(0) == "!"){
alert(exception.substr(1));
document.form1.txtNum1.focus();
document.form1.txtNum1.select();
}
else alert(exception);
}
else alert("The following error occurred: " + exception.message);
}
}
</script>
</head>
<body>
<form action="" name="form1">
<input type="text" name="txtNum1" size="3" /> factorial is
<input type="text" name="txtResult" size="25" /><br/>
<input type="button" value="Calculate Factorial"
name="butCalculate" onclick="butCalculate_onclick()" />
</form>
</body>
</html>
This happens because Chrome doesn't allow frames from your hard disk to access each others' content. Which, technically we term as Cross-origin request.
Solution of the above problem is:
1. Either you host your webpage on a local web server. See the following link:
What is a faster alternative to Python's http.server (or SimpleHTTPServer)?
2. Use any other browser like Firefox
If you use Visual Studio Code, you can install an extension named "Live Server". It helped me when I had the same problem.
If you don't want to use a local web server as suggested in the accepted answer you can run the browser with cross domain web security / same origin policy disabled.
For Chrome:
Disable same origin policy in Chrome
For Firefox:
Disable cross domain web security in Firefox
https://addons.mozilla.org/en-US/firefox/addon/access-control-allow-origin/
Because of the 'Cross-origin' request, the 'blocked a frame with origin "null" from accessing a cross-origin frame' error occurs. There are several workarounds to this problem, such utilising a 'local web server' or using a browser with 'cross domain web security' deactivated, to name a few. This article will go over all of the options for dealing with cross-origin concerns.
Refer to this link:
https://kodlogs.net/195/blocked-a-frame-with-origin-null-from-accessing-a-cross-origin-frame