how to make javascript functions together?

Question

Below is the JavaScript code I use in my HTML page

<script type="text/javascript">
function loadXMLDoc(HTTP)
{
    var xmlHttp;
    try {  
        xmlHttp=new XMLHttpRequest();
    } catch (e) { 
        try {    
            xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");   
        } catch (e) {   
            try {     
                xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");   
            } catch (e) {      
                alert("Your browser does not support AJAX!");      
                return false; 
            }    
        } 
    }

    xmlHttp.onreadystatechange=function() {
        if (xmlHttp.readyState==4) {
            alert(xmlHttp.responseText);
        }
    }  

    var params ="dd=123";
    xmlHttp.open("POST",HTTP,true);
    xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlHttp.setRequestHeader("Content-length", params.length);
    xmlHttp.setRequestHeader("Connection", "close");
    xmlHttp.send(params);
}
</script>

in the below javascript i wand to activate each ajax function

<script type="text/javascript">

// here i wand to send function together
return (loadXMLDoc('Page1.asp') && loadXMLDoc('Page2.asp') && loadXMLDoc('Page3.asp')); 
</script>

But here the problem is that I do not get the "return" (means 2nd & 3rd function not work)

Only the first function works

Hoping for your response

Mutation Person · Accepted Answer · 2010-02-21 15:51:36Z

1

Remeber that in the statement:

return (loadXMLDoc('Page1.asp') && loadXMLDoc('Page2.asp') && loadXMLDoc('Page3.asp'));

logically translates to:

if (loadXMLDoc('Page1.asp')){
    if (loadXMLDoc('Page2.asp')){
        if (loadXMLDoc('Page3.asp')){
            return true;
        }
    }
}
return false;

So, each of the successive loadXMLDoc() function calls will only be called when if the previous function returns true.

answered Feb 21, 2010 at 15:51

Mutation Person

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2 Comments

Alex Over a year ago

i try like this .. but only the first function work .. other not working

Andy E Over a year ago

@Alex: What he means is, you need to change that line of code to a proper sequential set of function calls, such as loadXMLDoc('Page1.asp'), loadXMLDoc('Page2.asp'), loadXMLDoc('Page3.asp');. Lose the return part of the statement too, it makes no sense in the global context.

Lachlan Roche · Accepted Answer · 2010-02-21 21:04:38Z

1

Your function loadXMLDoc() does not return anything, add "return true" to the end of that function.

    xmlHttp.send(params);

    return true;
}

Note that a true return from loadXMLDoc() means you have successfully started an AJAX request. It will finish some time in the future, which will result in the onreadystatechange being called. Thus you are starting multiple AJAX requests in parallel.

If you wanted several AJAX calls in sequence, try something like the following:

function doAjaxRequest( url, onreadystatechange )
{
    var xmlHttp;
    try {  
        xmlHttp=new XMLHttpRequest();
    } catch (e) {
        try {    
            xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");   
        } catch (e) {   
            try {     
                xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");   
            } catch (e) {      
                alert("Your browser does not support AJAX!");      
                return false; 
            }    
        } 
    }

    xmlHttp.onreadystatechange = onreadystatechange;

    var params = "dd=123";
    xmlHttp.open("POST", url, true);
    xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlHttp.setRequestHeader("Content-length", params.length);
    xmlHttp.setRequestHeader("Connection", "close");
    xmlHttp.send(params);
}

function loadXMLDocs( HTTP )
{
    var loadNextFile = function() {
        if (HTTP.length != 0) {
            var url = HTTP.unshift();
            doAjaxRequest( url, onreadystatechange );
        }
    }

    var onreadystatechange = function() {
        if (this.readyState==4) {
            alert(xmlHttp.responseText);

            loadNextFile();
        }
    }

    loadNextFile();
}

loadXMLDocs( ['Page1.asp', 'Page2.asp', 'Page3.asp'] );

edited Feb 21, 2010 at 21:04

answered Feb 21, 2010 at 15:39

Lachlan Roche

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2 Comments

Alex Over a year ago

if i add return in the if(xmlHttp.readyState==4) { alert(xmlHttp.responseText); return true; } the function is not work together

Alex Over a year ago

and also i not get return true from the ajax

Daniel Magnusson · Accepted Answer · 2010-02-21 15:46:20Z

0

Wow talk about indentation hell. this should work better;

<script type="text/javascript">
function loadXMLDoc(HTTP){
var xmlHttp;
try{  
    xmlHttp=new XMLHttpRequest();  }
    catch (e){ 
        try{    
            xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");   
        }catch (e){   
            try{     
                xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");   
            }catch (e){      
                alert("Your browser does not support AJAX!");      
                return false; 
            }
        }
    }
    xmlHttp.onreadystatechange=function(){
        if(xmlHttp.readyState==4){
            alert(xmlHttp.responseText);
        }
    }   
    var params ="dd=123";
    xmlHttp.open("POST",HTTP,true);
    xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlHttp.setRequestHeader("Content-length", params.length);
    xmlHttp.setRequestHeader("Connection", "close");
    xmlHttp.send(params);

    return true;
}
</script>

answered Feb 21, 2010 at 15:46

Daniel Magnusson

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1 Comment

Alex Over a year ago

xmlHttp.send(params); return true; ajax function is braking here , we not get response

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