我尝试过自己做这件事，甚至阅读了其他人对此练习的解决方案，但我就是不明白。我需要有人给我关于如何使删除按钮发挥作用的建议。这就是我到目前为止所做的
var button = document.getElementById("enter");
var input = document.getElementById("userinput");
var ul = document.querySelector("ul");
var buttonDlt = document.querySelectorAll("delete");
function inputLength() {
return input.value.length;
}
function createListElement() {
var li = document.createElement("li");
li.appendChild(document.createTextNode(input.value));
ul.appendChild(li);
input.value = "";
}
function addListAfterClick() {
if (inputLength() > 0) {
createListElement();
}
}
function addListAfterKeypress(event) {
if (inputLength() > 0 && event.keyCode === 13) {
createListElement();
}
}
function deleteAfterClick() {
li.remove(button.addEventListener("click"));
}
button.addEventListener("click", addListAfterClick);
buttonDlt.addEventListener("click", deleteAfterClick);
input.addEventListener("keypress", addListAfterKeypress);<!DOCTYPE html>
<html>
<head>
<title>Javascript + DOM</title>
<link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
<h1>Shopping List</h1>
<p id="first">Get it done today</p>
<input id="userinput" type="text" placeholder="enter items">
<button id="enter">Enter</button>
<ul>
<li class="bold red" random="23">Notebook <button class="delete">Delete</button> </li>
<li>Jello <button class="delete">Delete</button></li>
<li>Spinach <button class="delete">Delete</button></li>
<li>Rice <button class="delete">Delete</button></li>
<li>Birthday Cake <button class="delete">Delete</button></li>
<li>Candles <button class="delete">Delete</button></li>
</ul>
<script type="text/javascript" src="script.js"></script>
</body>
</html>我添加了事件监听器，声明了所有涉及的变量和元素。我无法弄清楚我错过了什么......
最佳答案
您有:var buttonDlt = document.querySelectorAll("delete");，它返回一个节点列表(匹配元素的集合)。集合没有 .addEventListener() 方法，因此这一行:
buttonDlt.addEventListener("click", deleteAfterClick);
失败，因此当您单击删除按钮时不会发生任何事情。
您需要做的是迭代集合中的所有项目并将它们绑定(bind)到删除事件处理程序，或者您可以在更高级别处理该事件，然后确定哪个元素触发了该事件并采取相应的操作。这种方法称为 "event delegation"并导致更少的代码(无需循环遍历集合并向每个项目注册事件处理程序)和更好的性能(而不是许多事件注册，只有一个)。此外，当应具有事件绑定(bind)的新元素动态添加到文档中时(就像您在此处创建新的购物列表项目一样)，这种方法是首选，因为这些新项目不必使用显式事件处理程序进行设置。
此外，删除项目的代码:
li.remove(button.addEventListener("click"));
不正确。
请参阅下面的内联评论:
var button = document.getElementById("enter");
var input = document.getElementById("userinput");
var ul = document.querySelector("ul");
function inputLength() {
return input.value.length;
}
function createListElement() {
var li = document.createElement("li");
li.appendChild(document.createTextNode(input.value));
// Create a delete button and configure it:
var btnDelete = document.createElement("button");
btnDelete.classList.add("delete");
btnDelete.textContent = "Delete";
// Append the button to the list item
li.appendChild(btnDelete);
ul.appendChild(li);
input.value = "";
}
function addListAfterClick() {
if (inputLength() > 0) {
createListElement();
}
}
function addListAfterKeypress(event) {
if (inputLength() > 0 && event.keyCode === 13) {
createListElement();
}
}
function deleteAfterClick(event) {
// Determine if it was a delete button that was clicked
if(event.target.classList.contains("delete")){
// Remove the closest li ancestor to the clicked element
event.target.closest("li").remove();
}
}
button.addEventListener("click", addListAfterClick);
// keypress is deprecated, use keydown instead
input.addEventListener("keydown", addListAfterKeypress);
// Handle all the clicks that originate from within the <ul> at
// the <ul> level when they bubble up to it instead of setting each
// button within the <ul> up with its own click event handler.
ul.addEventListener("click", deleteAfterClick);<!DOCTYPE html>
<html>
<head>
<title>Javascript + DOM</title>
<link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
<h1>Shopping List</h1>
<p id="first">Get it done today</p>
<input id="userinput" type="text" placeholder="enter items">
<button id="enter">Enter</button>
<ul>
<li class="bold red" random="23">Notebook <button class="delete">Delete</button> </li>
<li>Jello <button class="delete">Delete</button></li>
<li>Spinach <button class="delete">Delete</button></li>
<li>Rice <button class="delete">Delete</button></li>
<li>Birthday Cake <button class="delete">Delete</button></li>
<li>Candles <button class="delete">Delete</button></li>
</ul>
</body>
</html>关于javascript - 在 JavaScript 中创建删除按钮以删除购物 list 项目，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/59506089/