Ajax question - responseText return a javascript code but browser can't run it - help

**kevin31** · 06-17-2006 12:16 AM

Hello!

Please look at my code below

File index.html

HTML Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> Test Ajax </TITLE>
<script language=javascript>
//============
function createRequest() {
	var request = null;
	try {
		request = new XMLHttpRequest();
	} 
	catch (trymicrosoft) {
		try {
			request = new ActiveXObject("Msxml2.XMLHTTP");
		} 
		catch (othermicrosoft) {
			try {
				request = new ActiveXObject("Microsoft.XMLHTTP");
			} 
			catch (failed) {
				request = null;
			}
		}
	}

    return request;

}

//============
var request_call_alert = createRequest();
function call_alert(){
	url = "index.php";
	request_call_alert.open("GET", url, true);
	request_call_alert.onreadystatechange = call_alert2;
	request_call_alert.send(null);
}
function call_alert2(){
	if (request_call_alert.readyState == 4) {
	    if (request_call_alert.status == 200) {
			var result = request_call_alert.responseText;
			document.getElementById("object").innerHTML = result;
		}
	}
}

</script>
</HEAD>

<BODY>

<form>
<div id=object></div>
<input type="button" value="Call Ajax Alert" onClick="call_alert();">
</form>

</BODY>
</HTML>

And here is my PHP script
index.php

PHP Code:


<?

print "<b>Javascript Alert</b>";

print "<script language=javascript>alert('How to make this alert works?')</script>";

?>

As you can see responseText will return the HTML code

HTML Code:

<b>Javascript Alert</b><script language=javascript>alert('How to make this alert works?')</script>

So when I click button "Call Ajax Alert" , all I see is the text Javascript Alert - I don't see the pop up alert.

I need your help to make this alert work.

Thanks.
Kevin

**phpnovice** · 06-17-2006 08:08 AM

The problem with JavaScript code, received via an Ajax call, is that it is received as a text string and I'm not aware of any formal method for telling the browser to invoke the JavaScript Engine and, thus, turn that text string into executable JavaScript code. Did you notice that I said "formal" method, though.

The only "informal" method I'm aware of (that works) is using the eval() method.

**netbuddy** · 06-17-2006 08:24 AM

eval() is a very useful and easily abused function.

eval is your portal into the JScript / JavaScript engine, you poke it with VALID code and the interpreter will run that section of code, you can easily run into trouble with misuse of it, so you MUST limit its use and take care when using it...

Code:

var y = 'prompt("Hi what is your name?","");';
var x = eval(y);
document.write('Hello ' + x);

**kevin31** · 06-17-2006 08:48 AM

Thanks for your reply. But I still can't make this alert work with eval().

I modified my index.php script like this:

PHP Code:


<?php

print<<<EOF

<b>Call Alert</b>

<script language=javascript>

var y = 'prompt("Hi what is your name?","");';

var x = eval(y);

document.write('Hello ' + x);

</script>

EOF;

?>

Any idea? Thanks

Kevin

**phpnovice** · 06-17-2006 08:54 AM

What DOCTYPE are you using? Perhaps this:

<script language=javascript>

should be this:

<script type="text/javascript">

**netbuddy** · 06-17-2006 09:00 AM

I thought that you want a script returned by an AJAX request to be run in the browser.

if you take the responseText value that is returned and pass it to eval() the script will run if the code is VALID!

The example I p[osted was to demonstrate that the value in the string was script and that eval when it recieved it ran the script and returned a value.

that should be more than enough for you to achieve your goal.

**Svenito** · 10-20-2008 10:17 AM

Sorry to revive a VERY old topic, but it's relevant to my question:

I'm doing pretty much what the rest of this thread is describing. Once I get the readyState == 4 and have my response rendered, I call a function that gets the elements with name "scripts" in my response and then passes the innerHTML to eval.
This works if the innerHTML contains only alert("test"); but the problem is that it also prints the text "alert("test");" to the page, as well as evaluating it. If I wrap it in script tags it no longer print but doesn't execute either.

What's the right way of executing the script code without printing it to the page.

My response is from a PHP script.

**Dok** · 10-20-2008 11:04 AM

The JavaScript code you recieve in responseText is just text. To have the browser interpret the responseText as JavaScript you need to eval it. Its very simple...you just do

Code:

if (xhr.readyState == 4)
  eval(xhr.responseText);

An example of how eval works

Code:

// A string
var s = 'function test(){alert("Hello world"};';
// Now eval the string
eval(s);
// The function test is now available
test();  // Output is 'Hello world'

**Svenito** · 10-20-2008 11:14 AM

I wasn't clear enough in my previous post, sorry. The problem is that I want part of the response rendered on the page, as well as some javascript on the page as well, that is generated from the PHP.

I got this working by wrapping the script sections in tags and then evaluating only those bits of the response, and then additionally also setting the display style to 'none' to stop it printing. If I don't set it to display:none then the script sections get evaluated by eval AND get printed on the page

I'm not sure this the correct way of doing it, but the results are what I need.

**Dok** · 10-20-2008 12:29 PM

I would recommend using 2 separate requests but if you insist on 1 then do something like

Code:

var s = '<div>some html</div>[JS]function test(){some JS}';
// Split the string at [JS]
var s = s.split('[JS]');

Now s[0] is the HTML and s[1] is the javascript.

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