Java script function returning undefined

pratik.itworld · 10-20-2010, 04:18 PM

I have a function where in I call another function that assigns a value to a var.

e.g.

Code:

function setVar{
   var thisVar = 'hello';
   return thisVar;
}
function callFuncSetVar {
   var newVar = setVar();
  alert(newVar);
}

For some reason my code below is returning 'undefined'. But when I place an alert(); before the 'return' it shows the correct value. However when I place an alert(); to show the var that is set to what the function returns it says 'undefined'.

Firebug throws no errors. I am using a little bit of jQuery.

abduraooft · 10-20-2010, 04:23 PM

Quote:

function setVar{
var thisVar = 'hello';
return thisVar;
}
function callFuncSetVar {
var newVar = setVar();
alert(newVar);
}

That should be

Code:

function setVar(){
var thisVar = 'hello';
return thisVar;
}
function callFuncSetVar (){
var newVar = setVar();
alert(newVar);
}

Philip M · 10-20-2010, 04:24 PM

pratik.itworld · 10-20-2010, 04:27 PM

Quote:

Originally Posted by abduraooft

That should be

Code:

function setVar(){
var thisVar = 'hello';
return thisVar;
}
function callFuncSetVar (){
var newVar = setVar();
alert(newVar);
}

Hey sorry,
That was a typo. I have mentioned the brackets in ma original code.... Any other solution please

Philip M · 10-20-2010, 04:31 PM

That code (and the same code in Post#2) works just fine for me in all browsers.

pratik.itworld · 10-20-2010, 04:35 PM

This is my real code

Code:

function mobile_validate(){ 
	
	  var j=/^[0-9]+$/;
	  if(document.getElementById('mobile').value.match(j)){
	  }else{
		  alert('Please enter only Number.');
		  document.getElementById('mobile').focus();
		  return false;
	 }
	 if(document.getElementById("mobile").value.indexOf("0")==0){
		 alert("Please do not use 0 at the begining of the mobile number.");
		 document.getElementById("mobile").focus();
		 return false;
	 }
	 var k=document.getElementById("mobile").value.charAt(0);
	 if(k!=9&&k!=8&&k!=7){
		 alert("Your mobile number should begin either with 7 or 8 or 9");
		 document.getElementById("mobile").value ="";
		 document.getElementById("mobile").focus();
		 return false;
	 }
	 m = document.getElementById('mobile').value.length;
	 if(m>0&&m!=10){
		 alert("Please enter your 10 digit mobile number.");
		 document.getElementById("mobile").value ="";
		 document.getElementById("mobile").focus();
		 return false;
	 }
	var mobile_Request;  
	var mobile_val;
	mobile_Request = new GetXmlHttpObject();
	mobile_Request.onreadystatechange = function(){
		if(mobile_Request.readyState == 4){
			var mobileDisplay = mobile_Request.responseText;
			if(mobileDisplay == '2'){
				document.getElementById('mobile_err').innerHTML = "<b>Mobile already exists.</b>";
				//mobile_val = "1";		//alert(mobile_val);
				return 1;
			}else{
				document.getElementById('mobile_err').innerHTML = "<span style='padding:0px;'><img src='images/right1.jpg'/></span>";
				mobile_val = 0;
				return mobile_val;
			}
		}
	}

	 var mobile    =  document.getElementById('mobile').value;
	 var para_mobile = "?mobile="+mobile;
	 mobile_Request.open("GET", "get_mobile.php"+para_mobile, true);
	 mobile_Request.send(null); 
	
}


function ajaxFunction() {

 var mv = mobile_validate();
alert(mv);
}

Here alerting the value of mv is giving me "undefined" value
Please help me with this

Philip M · 10-20-2010, 05:14 PM

Stripped down it still seems to work:-

Code:

<script type = "text/javascript">
function mobile_validate(){ 
var mobile_val;
mobile_val = "1"; 
alert (mobile_val);
return mobile_val;
}

function ajaxFunction() {
var mv = mobile_validate();
alert ("MV = " + mv);
}


ajaxFunction();
</script>

What does Firebug say?

pratik.itworld · 10-20-2010, 05:22 PM

Hi Philip, The above script worked fine. But my mobile_validate is an ajax function. And my original script is still returning "undefined"

siberia-man · 10-20-2010, 05:42 PM

Quote:

Originally Posted by pratik.itworld

this is my real code

Code:

function mobile_validate(){ 
...
	var mobile_val;
	mobile_request = new getxmlhttpobject();
	mobile_request.onreadystatechange = function(){
		if(mobile_request.readystate == 4){
			var mobiledisplay = mobile_request.responsetext;
			if(mobiledisplay == '2'){
...
				//mobile_val = "1";		//alert(mobile_val);
				return 1;
			}else{
...
				mobile_val = 0;
				return mobile_val;
			}
		}
	}
...
}
...

here alerting the value of mv is giving me "undefined" value
please help me with this

Look here! I have removed all insensitive lines from your code and kept essential only. Let's consider them in their order.
1. the internal variable mobile_val is defined
2. the callback function mobile_request.onreadystatechange is defined. It will set this variable when readystate will changed to 4 (a document is loaded and ready to use).
3. Other lines attempt to set this variable or return some valie that should be set.

So mobile_request.onreadystatechange does not return any value. It is used to make somthing on different stages of a document loading. In your case it should set the variable mobile_val = something

After that the outer function mobile_validate should return this value like this -- return mobile_val;.

As a conclusion. your function can look like below:

Code:

function mobile_validate()
{
	var return mobile_val;
...
	mobile_request.onreadystatechange = function()
	{
....
		mobile_val = ...
...
	}
...
	return mobile_val;
}

You understand that I show the essential lines only. I have many critical points over this code related optimality of it's algorithm but there will be so many words so recently I keep your attention to the main problem.

siberia-man · 10-20-2010, 05:56 PM

Ohhh! You are using asynchronous request. This means that the outer function will never return something else excepting 'undefined'.

pratik.itworld · 10-20-2010, 06:02 PM

Thanks for your solutions guys...
But i resolved the problem.
The issue was.. as I m sending the ajaxRequest.send(null) it is making all the variables undefined...
so i returned the value aftr the ajaxRequest.send(null) and it startd working..

zwhitchcox · 12-06-2012, 05:03 AM

You have to put the onreadystatechange function after the send request, and you ALSO have to set the open() third parameter to false, to make it synchronous.