change variable value in event handler function

Question

I'm trying to change my gaTop var in my functiontest but I don't understand why it doesn't work

var gaTop = 0;

functionTest = function(callback)
{
    $('html').on("mousewheel DOMMouseScroll", function(e)
    {
        var delta = (e.originalEvent.wheelDelta || -e.originalEvent.detail);

        if (delta < 0)
        {
            var gaTop = -100;
        }
        else if (delta > 0)
        {
            var gaTop = +100;
        }

        console.log(gaTop);

        callback(gaTop);
    });
}

functionTest(function(e)
{
    console.log(gaTop);
});

your declaring and initializing gaTop in every block and you are not using ga. — Rajashekhar
– Rajashekhar, Commented Dec 27, 2016 at 14:22
You have to make gaTop as a global variable or declare it in such a scope where both function can access it — Kiran Shinde
– Kiran Shinde, Commented Dec 27, 2016 at 14:24

Community · Accepted Answer · 2017-05-23 11:46:01Z

1

As reference: Declaring vs Initializing a variable?

var ga = 0;
var gaTop = null;
functionTest = function(callback) {
$('html').on("mousewheel DOMMouseScroll", function(e) {
  var delta = (e.originalEvent.wheelDelta || -e.originalEvent.detail);
  if (delta < 0) {
    gaTop = -100;
  } 
  else if (delta > 0) {
    gaTop = 100;
  }
  console.log(gaTop);
  callback(gaTop);

});
}
functionTest(function(e) {
 console.log(gaTop);
});

edited May 23, 2017 at 11:46

CommunityBot

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answered Dec 27, 2016 at 14:26

serkan

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1 Comment

user7346183 Over a year ago

i'm sorry i did a mistake, my var ga should be gaTop. But the console.log(gaTop) always return 0

Balaji Marimuthu · Accepted Answer · 2016-12-27 14:28:22Z

0

Initialize the variable at top before assign the value. otherwise it won't set, you are creating new variable and set the value in both if and else part that is the cause of issue.

var gaTop = null;
 if (delta < 0) {
     gaTop = -100;
  } 
  else if (delta > 0) {
    gaTop = +100;
  }

answered Dec 27, 2016 at 14:28

Balaji Marimuthu

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2 Comments

user7346183 Over a year ago

i'm sorry i did a mistake, my var ga should be gaTop. But the console.log(gaTop) always return 0

Balaji Marimuthu Over a year ago

debug and verify the delta value in on mousewheel event

user7346183 · Accepted Answer · 2016-12-27 14:57:28Z

0

its finally working, thanks for your help !

var gaTop = 0;

            functionTest = function(callback) {
            $('html').on("mousewheel DOMMouseScroll", function(e) {
              var delta = (e.originalEvent.wheelDelta || -e.originalEvent.detail);
              if (delta < 0) {
                gaTop = gaTop -100;
              } 
              else if (delta > 0) {
                gaTop = gaTop +100;
              }
              callback(gaTop);

            });
            }
            functionTest(function(e) {
             console.log(gaTop);
            });

answered Dec 27, 2016 at 14:57

user7346183

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