javascript - 更改事件处理函数中的变量值

Question

我正在尝试更改 functiontest 中的 gaTop var，但我不明白为什么它不起作用

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);
});

Answer 1

引用: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);
});