jQuery on，只添加一个事件监听器

Question

我有一个ul的事件监听器：

$('body').on('click.submenu', '.top-level', subMenu);

有没有办法确保只添加一次？

原因是，当视口处于“移动”断点时，我只需要添加它，当它从桌面回到移动时，似乎有多个事件监听器。

Answer 1

var body = $("body");                             //Store for later use
if(!(body.data("EventAdded") === true)){            //Test if event was added
    body.data("EventAdded", true)                     //If not, set EventAdded as true
        .on('click.submenu', '.top-level', subMenu);  //and add the event
}

Answer 2

我唯一能想到的就是在添加监听器之前调用off

$('body').off('click.submenu', '.top-level', subMenu);
$('body').on('click.submenu', '.top-level', subMenu);