javascript - Esc 事件监听器不起作用

Question

我已经添加了按键监听器，但这不起作用。当“click”的监听器被调用时 - 工作完美。

这是代码:

var closeSave = document.getElementById("closeSave");
    closeSave.addEventListener("click", closeWindow);
    closeSave.addEventListener("keypress", closeWindowByEsc);

            // When the user clicks on <span> (x), close the modal
        var closeWindow = function() {
            saveModal.style.display = "none";
            loadModal.style.display = "none";
        }

    var closeWindowByEsc = function(){
    if (!e) e = window.event;
    var keyCode = e.keyCode || e.which;
    if (keyCode == '27'){
      closeWindow(e);
    }
  }

可能是什么问题？

Answer 1

问题在于声明 var func = function () { ... 将 var func; 部分提升到作用域的顶部，但是 func在到达该行之前， 不会被定义为 function () { ...。因此，当您附加事件处理程序时，基本上会发生以下情况:

var closeSave = document.getElementById("closeSave");
var closeWindow;
var closeWindowByEsc;

// here, closeWindow and closeWindowByEsc are `undefined`
closeSave.addEventListener("click", closeWindow);
closeSave.addEventListener("keypress", closeWindowByEsc);

// When the user clicks on <span> (x), close the modal
closeWindow = function() {
  saveModal.style.display = "none";
  loadModal.style.display = "none";
}

closeWindowByEsc = function(e) {
  if (!e) e = window.event;
  var keyCode = e.keyCode || e.which;
  if (keyCode == '27') {
    closeWindow();
  }
}

您可以做两件事来解决这个问题:

将 addEventListener() 移至实例化下方:

var closeSave = document.getElementById("closeSave");

// When the user clicks on <span> (x), close the modal
var closeWindow = function() {
  saveModal.style.display = "none";
  loadModal.style.display = "none";
}

var closeWindowByEsc = function(e) {
  if (!e) e = window.event;
  var keyCode = e.keyCode || e.which;
  if (keyCode == '27') {
    closeWindow();
  }
}

closeSave.addEventListener("click", closeWindow);
closeSave.addEventListener("keypress", closeWindowByEsc);

或者您可以使用将实例化提升到作用域顶部的函数语句，而不是函数表达式:

var closeSave = document.getElementById("closeSave");

closeSave.addEventListener("click", closeWindow);
closeSave.addEventListener("keypress", closeWindowByEsc);

// When the user clicks on <span> (x), close the modal
function closeWindow() {
  saveModal.style.display = "none";
  loadModal.style.display = "none";
}

function closeWindowByEsc(e) {
  if (!e) e = window.event;
  var keyCode = e.keyCode || e.which;
  if (keyCode == '27') {
    closeWindow();
  }
}