Javascript Function always returns wrong value, although variable had correct values before

Question

I have a function that returns the highest value of an attribute in an xml file

The Value returned is always 0, so I think the value under the JQuery function doesnt know what happens inside of it. Here is the function:

function findHighestValue(url,attr){
var highestValue = 0;
$.ajax({
    type: "GET",
    url: url,
    dataType: "xml",
    success: function(xml) {
        $(xml).find("achievement").each(function(){
             var value = $(this).find(attr).text();
             value = value*1;//typecast
             console.log("value: "+value);//shows correct value
             console.log("highestValue in ajax: "+highestValue);//shows correct value
             if (value >= highestValue){
                 highestValue = value;
                 console.log("Value higher highesValue detected!");//works as intended
             }

        });
    }
});
console.log("Highest Value: "+highestValue);// is 0 again
return highestValue;//always returns 0
}

Richard Dalton · Accepted Answer · 2012-04-05 09:03:00Z

6

As it's an ajax request the last two lines are hit before the lines inside the success method.

You cannot return a value from an ajax request unless you set async: false

You need to process the value via the success callback rather than trying to return it.

answered Apr 5, 2012 at 9:03

Richard Dalton

35.8k6 gold badges75 silver badges92 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

最白目 Over a year ago

I learned my lesson, it makes totally sense. I set the async to false and now it works as intendted. Thank you!

Richard Dalton Over a year ago

@dan I don't advise setting async to false though as this will freeze the browser if your ajax request takes a long time. Much better to use the callback function to perform your logic.

Andreas Wong · Accepted Answer · 2012-04-05 09:02:21Z

2

AJAX is asynchronous, thus it doesn't wait for your $.ajax() call before calling console.log(), hence the wrong value. So you are right in the sense that doesnt know what happens inside of it

To tackle this, you can either place the rest of your function's logic inside success property of your $.ajax call or set async: false, be warned though that your browser will "freeze" a bit when $.ajax() happens

answered Apr 5, 2012 at 9:02

Andreas Wong

60.7k19 gold badges112 silver badges123 bronze badges

Collectives™ on Stack Overflow

Javascript Function always returns wrong value, although variable had correct values before

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related