我正在尝试创建一个站点,可以在其中将对象添加到列表中,然后通过按钮删除。目前,programm可以添加到列表中并具有其他一些功能,但是我无法为按钮创建"删除"功能。我几乎明白为什么:当我单击附加的按钮时,我为列表创建的功能(单击时的行通和文本颜色)正在响应,因为它认为它属于列表。特别是,错误是:
script.js:55 Uncaught TypeError: Cannot read property 'classList' of undefined
at toggle (script.js:55)
at HTMLUListElement.whenClicked (script.js:65)
但问题是,我能找到的问题的唯一解决方案是重写整个程序,并使其更加复杂:我可以创建一个用 HTML 编写的li
对象的数组,然后将它们通过 while 循环附加到ul
并在同一循环中附加按钮,所以它们不会是一个对象。这就是为什么我向你们所有人寻求帮助。有人可以建议我如何解决我们最终使一切变得如此复杂的情况吗?提前谢谢。
法典
注意:我创建了一个addButton功能的副本,以查看我是否可以在ul
末尾使用按钮,但是它对用户不友好太多,这就是为什么它在评论中。此外,还有小deleteLi
功能,支持在addButton
函数中调用,以便按钮可以删除li
。
var button = document.getElementById("button");
var modify_list = document.getElementById("userinput");
var ul = document.querySelector("ul");
var li = document.querySelectorAll("li");
var i = 0; //Stored value so we can acces to it later in the function
while (li.length > i) {
li[i].classList.add(i);
li[i].classList.add('done');
li[i].classList.add('cursor');
i++
}
var n = 0
while (li.length > n){
li[n].classList.toggle("done");
n++
}
function inputLength(){
return modify_list.value.length;
}
function addToTheList(){
var li = document.createElement("li");
li.appendChild(document.createTextNode(modify_list.value));
ul.appendChild(li);
// createNewButton();
modify_list.value = '';
}
function addAfterClick(){
if (inputLength() === 0){
alert("Please,don't enter the empty list");
}else {
addToTheList();
}
}
function addAfterEnter(key){
if (key.keyCode === 13 && inputLength() > 0){
addToTheList();
}
}
button.addEventListener("click", addAfterClick);
modify_list.addEventListener("keypress", addAfterEnter);
function toggle(number){
li[number].classList.toggle("done");
}
ul.addEventListener("click", whenClicked);
function whenClicked(event){
var li_number = event.target.className[0];
//In JS it doesn't matter in some occasions if it's a string or number,I suppouse.
// var li_number = Number(li_number_string);
// console.log(li_number);
toggle(li_number);
}
// Create buttons and their functions
function addButton(list_number) {
var localButton = document.createElement("button");
var br = document.createElement("br");
localButton.innerText = "Delete";
localButton.id = "myButton" + list_number;
li[list_number].appendChild(br);
li[list_number].appendChild(localButton);
localButton.onclick = deleteLi(list_number);
}
// function addButton() {
// var localButton = document.createElement("button");
// localButton.innerText = "Delete";
// localButton.id = "myButton" + list_number;
// ul.appendChild(localButton);
// // localButton.onclick = deleteLi(list_number);
// }
var list_number = 0
// creates buttons for the li that were already created
while (li.length > list_number){
addButton(list_number);
list_number++;
}
// creates buttons for new li items.
function createNewButton(){
var number = window['list_number'];
addButton(number);
window['list_number'] = number + 1;
}
function deleteLi(list_number){
// var list_element = document.getElementById('myButton' + list_number)
ul.removeChild(ul.childNodes[list_number])
}
.done {
color: red;
text-decoration: line-through;
}
.cursor{
cursor: pointer;
}
<!DOCTYPE html>
<html>
<head>
<title>DOM</title>
<link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
<h1>What plans do I have till the end of the summer?</h1>
<p>They are:</p>
<input type="text" name="add activities" id ="userinput" placeholder="add activities">
<button id="button">Send</button>
<ul>
<li>Learn German</li>
<li>Learn Japanese</li>
<li>Learn Java Script</li>
<li>Physical activities</li>
</ul>
<script type="text/javascript" src="script.js"></script>
</body>
</html>
最后在addbutton函数中你应该做:localButton.onclick = () => deleteLi(list_number);
所以你必须将一个函数传递给onclik,而不是deleteLi的结果。