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, Dec 27 '16 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, Dec 27 '16 at 14:24

score 1 · Answer 1 · edited May 23 '17 at 11:46

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 '17 at 11:46

Community

1
1

answered Dec 27 '16 at 14:26

serkan

6,885
4
41
49

i'm sorry i did a mistake, my var ga should be gaTop. But the console.log(gaTop) always return 0 – user7346183 Dec 27 '16 at 14:49

score 0 · Answer 2 · answered Dec 27 '16 at 14:28

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 '16 at 14:28

Balaji Marimuthu

1,940
13
13

i'm sorry i did a mistake, my var ga should be gaTop. But the console.log(gaTop) always return 0 – user7346183 Dec 27 '16 at 14:49
debug and verify the delta value in on mousewheel event – Balaji Marimuthu Dec 27 '16 at 14:55

score 0 · Answer 3 · answered Dec 27 '16 at 14:57

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);
            });

change variable value in event handler function

3 Answers3