removeeventlistener 相关问题


具有多个值的JS var

有件事我无法理解: 我有一个打开同一页面的功能,但具有不同的内容,具体取决于菜单中单击的按钮: 有件事我无法理解: 我有一个打开同一页面的功能<div id="page">但具有不同的内容,具体取决于菜单中单击的按钮: <nav> <button onclick="openPage(1)">PAGE 1</button> <button onclick="openPage(2)">PAGE 2</button> <button onclick="openPage(3)">PAGE 3</button> </nav> 然后是函数: function openPage(p){ var move=0; // define a var for USER action if(p==1){ document.getElementById('page').innerHTML = text_1; // content preloaded } else if(p==2){ document.getElementById('page').innerHTML = text_2; } else if(p==3){ document.getElementById('page').innerHTML = text_3; } // then on the top of the page (absolute + z-index) I add a HTML object: document.getElementById('page').innerHTML += '<aside id="pictures">content</aside>'; // what I'm now trying to do is to remove this object once USER move its mouse on it document.getElementById('pictures').addEventListener("mousemove",function(event) { setTimeout(function(){ move+=1; // increase the val each second },1e3) console.log('move'+p+' = '+move) // control value if(move>100){ document.getElementById('pictures').style.display = "none"; // OK, it works move=0; // reinit the var } }); } 现在惊喜: 第 1 页的控制台 move1 = 0 move1 = 1 ... move1 = 99 move1 = 100 // 'pictures' disappears 第 2 页的控制台 move1 = 41 move2 = 0 ... move1 = 58 move1 = 17 ... move1 = 100 // 'pictures' disappears move2 = 59 第 3 页的控制台 move1 = 15 move2 = 88 move3 = 0 ... move1 = 37 move2 = 100 // 'pictures' disappears move3 = 12 ... 我的 var 'move' 同时获得 3 个值...这怎么可能? 您的问题的原因是您每次调用 openPage 函数时都会添加一个事件侦听器。这意味着,如果您单击多个按钮,每个按钮都会有自己的事件侦听器附加到 #pictures 元素。现在,当触发 mousemove 事件时,所有这些侦听器将同时执行,导致 move 变量每秒递增多次。 解决此问题的方法是在添加新事件侦听器之前先删除现有的事件侦听器。 let handler; // to hold the event listener function const pictureEl = document.getElementById('pictures'); function openPage(p){ // Remove existing event listener if (handler) { // <-- Check here pictureEl.removeEventListener("mousemove", handler); } handler = function(event) { // ...Rest } }; // Add new event listener pictureEl.addEventListener("mousemove", handler); // ...rest 找到了另一种(最简单的?)方法: var move=0; // placed out of functions function openPage(p){ .... (same as previous) getElementById('pictures').addEventListener("mousemove",outPicts); // change } // put mousemove event in another function: function outPicts(p){ setTimeout(function(){ move+=1; },1e3) console.log('move = '+move) if(move>100){ document.getElementById('pictures').style.display = "none"; // then remove event getElementById('pictures').removeEventListener("mousemove",outPicts); move=0; // reinit the var } } 按预期工作


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