addEvenListener在动态按钮上不起作用-javascript [英] addEvenListener doesn't work on dynamic button - javascript

问题描述

所以我目前正忙于学习JavaScript。我创建了一些动态按钮，并尝试向其添加addEvenListener。但这是行不通的，我无法弄清楚为什么行不通。我只是在测试一些东西，然后尝试使用本地存储中的值创建按钮。几乎可以正常工作，只有addEvenListener无法正常工作。我只想使用本地存储中的密钥发出简单警报。

So I'm currently busy with learning JavaScript. I created some dynamic buttons and I tried to add an addEvenListener to it. But it doesn't work and I can't figure it out why it doesn't work. I'm just testing some stuff and I try to create buttons with values from the localstorage. It is almost working, only the addEvenListener isn't working. I just want a simple alert with the key from the localstorage.

for (var i = 0; i <= localStorage.length-1; i++) {
    var categoryButton = document.createElement('input');
    categoryButton.setAttribute('class', 'forumMenu');
    categoryButton.setAttribute('type', 'button');
    categoryButton.setAttribute('name', localStorage.key(i));
    categoryButton.setAttribute('value', localStorage.key(i));
    categoryButton.setAttribute('id', localStorage.key(i));
    categoryButton.addEventListener('click', function(col){
    alert(col);
}(localStorage.key(i)),true);
    forumMenu.appendChild(categoryButton);
}

有人知道为什么它不起作用吗？

Does anyone know why it doesn't work?

推荐答案

您没有将函数传递给 EventTarget。 addEventListener（） 。您将立即执行并传递以下结果：

You're not passing a function to EventTarget.addEventListener(). You're immediately executing and passing the result of this:

function (col) {
  console.log(col);
}(localStorage.key(i))

...这是 未定义 。您可以使用以下语法对此进行修改：

... which is undefined. You can ammend that by using the following syntax:

categoryButton.addEventListener('click', (function(col) { 
   // return a function to addEventListener
   return function(){
      console.log(col);
   }
})(localStorage.key(i)),true);

这是一个演示：

var input;
for (var i = 0; i <= 5; i++) {
  input = document.createElement('input');
  input.type = "button"
  input.value = i;
  input.addEventListener('click', function(i) {
    // return a function to addEventListener
    return function() {
      console.log(i);
    }
  }(i), true);
  document.body.appendChild(input);
}

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