XMLHttpRequest() returning response in a function

Question

I have a function isOnline(), which looks like this:

function isOnline() {
    var request=new XMLHttpRequest(); 

    request.onreadystatechange=function() {
        if(request.readyState==4) {
            if(request.responseText=="online")
                return true;    
        }    
    }
    request.open("GET","onlinecheck.php?user=user",false);
    request.send();

    return false;
}

If I run document.write(isOnline()); for testing , I ALWAYS get false, (undefined if i dont write return false; , I get undefined.

How do I 'wait' before the readyState is 4 and return true after that ?

score 2 · Answer 1 · edited May 23 '17 at 12:27

You need to focus on few things:

onreadystatechange is used when sending an asynchronous request - more here.
So if you are trying to send an asynchronous request, use async=true in the call - read more here.
```
request.open("GET", "onlinecheck.php?user=user", true);
```
finally, if you are going to use asynchronous call, you can't return a value. Check these two links
1. Returning values from the event onreadystatechange in AJAX
2. How to return value from an asynchronous callback function?

In case you decide to do it synchronously:

function isOnline() {
    var request=new XMLHttpRequest(); 

    request.open("GET","www.google.com/",false);
    request.send();

    /* check the readyState, you can also check for status code */
    if (request.readyState === 4)
        // put other conditions here if you need to    
        return true;
    else
        return false;
}

// It returns true

XMLHttpRequest() returning response in a function

1 Answers1