由于函数 debounce 返回一个函数，你仍需要调用它：

Since the function debounce returns a function, you still need to call it:

$(window).on('scroll', function (e) {
    debounce(function() {
        var scrollTop = $(window).scrollTop();
        if (scrollTop > 50) {
            $('.title').addClass('fixedPosition');
        } else {
            $('.title').removeClass('fixedPosition');
        }    
    }()/*note the call here*/, 250);
});

这与将debounce逻辑包装在另一个函数中的功能不同，而函数 myLogic 将自动调用：

This is not the same as wrapping your debounce logic in another function whereas the function myLogic will be called automatically:

function myLogic(){
    var scrollTop = $(window).scrollTop();
    $('.title').toggleClass('fixedPosition', scrollTop > 50);
}

$(window).on('scroll', debounce(myLogic, 250));