JQuery - 事件委托 - 我的代码中发生了什么?
JQuery - Event Delegation - What is happening in my code?
我已经尽可能多地阅读了有关事件委托的内容,但我无法弄清楚为什么我的代码会以这种方式运行。当页面加载时,所有复选按钮都正常工作(在 2 类 之间切换)。每当我将新商品添加到购物清单时,复选按钮仅适用于该新商品。如果我添加第二个新项目,复选按钮适用于该新项目,即 4 个原始项目,但不适用于第一个新项目。如果我添加任何更多项目,它将不适用于前一项,但适用于前一项的所有项目。
如何让复选按钮适用于所有项目?
HTML...
<body>
<div class="container">
<h1>Shopping List</h1>
<form id="js-shopping-list-form">
<label for="shopping-list-entry">Add an item</label>
<input type="text" name="shopping-list-entry" id="shopping-list-entry" placeholder="e.g., broccoli">
<button type="submit">Add item</button>
</form>
<ul class="shopping-list">
<li>
<span class="shopping-item">apples</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
<li>
<span class="shopping-item">oranges</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
<li>
<span class="shopping-item shopping-item__checked">milk</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
<li>
<span class="shopping-item">bread</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
</ul>
</div>
<script
src="https://code.jquery.com/jquery-3.4.1.js"
integrity="sha256-WpOohJOqMqqyKL9FccASB9O0KwACQJpFTUBLTYOVvVU="
crossorigin="anonymous"></script>
<script src="script.js"></script>
</body>
</html>
CSS...
* {
box-sizing: border-box;
}
body {
font-family: 'Roboto', sans-serif;
}
button, input[type="text"] {
padding: 5px;
}
button:hover {
cursor: pointer;
}
#shopping-list-item {
width: 250px;
}
.container {
max-width: 600px;
margin: 0 auto;
}
.shopping-list {
list-style: none;
padding-left: 0;
}
.shopping-list > li {
margin-bottom: 20px;
border: 1px solid grey;
padding: 20px;
}
.shopping-item {
display: block;
color: grey;
font-style: italic;
font-size: 20px;
margin-bottom: 15px;
}
.shopping-item__checked {
text-decoration: line-through;
}
JS...
//Make the Check Button functional
function checkButton() {
$(".shopping-item-toggle").on("click", "span", function() {
$(this).closest("li").find(".shopping-item").toggleClass("shopping-item__checked");
})};
checkButton();
//Make the Delete Button functional
function delButton() {
$(".shopping-item-delete").on("click", function() {
$(this).parent().parent().remove();
})};
delButton();
//Create a variable called buttons to add the 2 buttons in function below
let buttons = "<div class='shopping-item-controls'><button class='shopping-item-toggle'>\
<span class='button-label'>check</span></button>\
<button class='shopping-item-delete'><span class='button-label'>delete</span></button></div>";
//Add new Item to List
$("#js-shopping-list-form").submit(function() {
let item = $("#shopping-list-entry").val();
if (item != "") { //As long as the input has text in it, run the function below
$(".shopping-list").append("<li>" + "<span class='shopping-item'>" + item + "</span>" + buttons + "</li>");
event.preventDefault();
checkButton();//Make the check button functional
delButton();//Make the delete button functional
} else { //if NO text is in the input, show this alert
alert("Must enter an item name!");
}
});
无论何时添加新项目,新的点击处理程序都会绑定到所有项目。这意味着页面上存在的项目可能会得到两个或更多重复的处理程序。如果两个处理程序绑定到一个项目,第一个将 toggleClass
打开 "checked" class,第二个将立即关闭 class。
要使用事件委托,我建议只绑定一次处理程序,并将它们绑定到页面上始终存在的祖先。
例如:
// Bind "check" and "delete" handlers to the ".shopping-list" ancestor.
$(".shopping-list").on("click", ".shopping-item-toggle span", function() {
$(this).closest("li").find(".shopping-item").toggleClass("shopping-item__checked");
});
$(".shopping-list").on("click", '.shopping-item-delete', function() {
$(this).parent().parent().remove();
});
// Create a variable called buttons to add the 2 buttons in function below
let buttons = "<div class='shopping-item-controls'><button class='shopping-item-toggle'>\
<span class='button-label'>check</span></button>\
<button class='shopping-item-delete'><span class='button-label'>delete</span></button>\
</div>";
//Add new Item to List
$("#js-shopping-list-form").submit(function(event) {
event.preventDefault();
let item = $("#shopping-list-entry").val();
if (item != "") { // If the input has text in it, add the new item
$(".shopping-list").append("<li>" + "<span class='shopping-item'>" + item + "</span>" + buttons + "</li>");
} else { //if NO text is in the input, show this alert
alert("Must enter an item name!");
}
});
* {
box-sizing: border-box;
}
body {
font-family: 'Roboto', sans-serif;
}
button,
input[type="text"] {
padding: 5px;
}
button:hover {
cursor: pointer;
}
#shopping-list-item {
width: 250px;
}
.container {
max-width: 600px;
margin: 0 auto;
}
.shopping-list {
list-style: none;
padding-left: 0;
}
.shopping-list>li {
margin-bottom: 20px;
border: 1px solid grey;
padding: 20px;
}
.shopping-item {
display: block;
color: grey;
font-style: italic;
font-size: 20px;
margin-bottom: 15px;
}
.shopping-item__checked {
text-decoration: line-through;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="container">
<h1>Shopping List</h1>
<form id="js-shopping-list-form">
<label for="shopping-list-entry">Add an item</label>
<input type="text" name="shopping-list-entry" id="shopping-list-entry" placeholder="e.g., broccoli">
<button type="submit">Add item</button>
</form>
<ul class="shopping-list">
<li>
<span class="shopping-item">apples</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">oranges</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item shopping-item__checked">milk</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">bread</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
</ul>
</div>
下面是添加新项目后如何触发多个处理程序的演示:
//Make the Check Button functional
function checkButton() {
$(".shopping-item-toggle").on("click", "span", function() {
let $item = $(this).closest("li").find(".shopping-item");
console.log('Check Handler ' + ($item.hasClass('shopping-item__checked') ? 'OFF' : 'ON'));
$item.toggleClass("shopping-item__checked");
})
};
checkButton();
//Make the Delete Button functional
function delButton() {
$(".shopping-item-delete").on("click", function() {
console.log('Delete Handler');
$(this).parent().parent().remove();
})
};
delButton();
//Create a variable called buttons to add the 2 buttons in function below
let buttons = "<div class='shopping-item-controls'><button class='shopping-item-toggle'>\
<span class='button-label'>check</span></button>\
<button class='shopping-item-delete'><span class='button-label'>delete</span></button></div>";
//Add new Item to List
$("#js-shopping-list-form").submit(function(e) {
event.preventDefault();
let item = $("#shopping-list-entry").val();
if (item != "") { //As long as the input has text in it, run the function below
$(".shopping-list").append("<li>" + "<span class='shopping-item'>" + item + "</span>" + buttons + "</li>");
checkButton(); //Make the check button functional
delButton(); //Make the delete button functional
} else { //if NO text is in the input, show this alert
alert("Must enter an item name!");
}
});
* {
box-sizing: border-box;
}
body {
font-family: 'Roboto', sans-serif;
}
button,
input[type="text"] {
padding: 5px;
}
button:hover {
cursor: pointer;
}
#shopping-list-item {
width: 250px;
}
.container {
max-width: 600px;
margin: 0 auto;
}
.shopping-list {
list-style: none;
padding-left: 0;
}
.shopping-list>li {
margin-bottom: 20px;
border: 1px solid grey;
padding: 20px;
}
.shopping-item {
display: block;
color: grey;
font-style: italic;
font-size: 20px;
margin-bottom: 15px;
}
.shopping-item__checked {
text-decoration: line-through;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="container">
<h1>Shopping List</h1>
<form id="js-shopping-list-form">
<label for="shopping-list-entry">Add an item</label>
<input type="text" name="shopping-list-entry" id="shopping-list-entry" placeholder="e.g., broccoli">
<button type="submit">Add item</button>
</form>
<ul class="shopping-list">
<li>
<span class="shopping-item">apples</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">oranges</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item shopping-item__checked">milk</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">bread</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
</ul>
</div>
我已经尽可能多地阅读了有关事件委托的内容,但我无法弄清楚为什么我的代码会以这种方式运行。当页面加载时,所有复选按钮都正常工作(在 2 类 之间切换)。每当我将新商品添加到购物清单时,复选按钮仅适用于该新商品。如果我添加第二个新项目,复选按钮适用于该新项目,即 4 个原始项目,但不适用于第一个新项目。如果我添加任何更多项目,它将不适用于前一项,但适用于前一项的所有项目。
如何让复选按钮适用于所有项目?
HTML...
<body>
<div class="container">
<h1>Shopping List</h1>
<form id="js-shopping-list-form">
<label for="shopping-list-entry">Add an item</label>
<input type="text" name="shopping-list-entry" id="shopping-list-entry" placeholder="e.g., broccoli">
<button type="submit">Add item</button>
</form>
<ul class="shopping-list">
<li>
<span class="shopping-item">apples</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
<li>
<span class="shopping-item">oranges</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
<li>
<span class="shopping-item shopping-item__checked">milk</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
<li>
<span class="shopping-item">bread</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle">
<span class="button-label">check</span>
</button>
<button class="shopping-item-delete">
<span class="button-label">delete</span>
</button>
</div>
</li>
</ul>
</div>
<script
src="https://code.jquery.com/jquery-3.4.1.js"
integrity="sha256-WpOohJOqMqqyKL9FccASB9O0KwACQJpFTUBLTYOVvVU="
crossorigin="anonymous"></script>
<script src="script.js"></script>
</body>
</html>
CSS...
* {
box-sizing: border-box;
}
body {
font-family: 'Roboto', sans-serif;
}
button, input[type="text"] {
padding: 5px;
}
button:hover {
cursor: pointer;
}
#shopping-list-item {
width: 250px;
}
.container {
max-width: 600px;
margin: 0 auto;
}
.shopping-list {
list-style: none;
padding-left: 0;
}
.shopping-list > li {
margin-bottom: 20px;
border: 1px solid grey;
padding: 20px;
}
.shopping-item {
display: block;
color: grey;
font-style: italic;
font-size: 20px;
margin-bottom: 15px;
}
.shopping-item__checked {
text-decoration: line-through;
}
JS...
//Make the Check Button functional
function checkButton() {
$(".shopping-item-toggle").on("click", "span", function() {
$(this).closest("li").find(".shopping-item").toggleClass("shopping-item__checked");
})};
checkButton();
//Make the Delete Button functional
function delButton() {
$(".shopping-item-delete").on("click", function() {
$(this).parent().parent().remove();
})};
delButton();
//Create a variable called buttons to add the 2 buttons in function below
let buttons = "<div class='shopping-item-controls'><button class='shopping-item-toggle'>\
<span class='button-label'>check</span></button>\
<button class='shopping-item-delete'><span class='button-label'>delete</span></button></div>";
//Add new Item to List
$("#js-shopping-list-form").submit(function() {
let item = $("#shopping-list-entry").val();
if (item != "") { //As long as the input has text in it, run the function below
$(".shopping-list").append("<li>" + "<span class='shopping-item'>" + item + "</span>" + buttons + "</li>");
event.preventDefault();
checkButton();//Make the check button functional
delButton();//Make the delete button functional
} else { //if NO text is in the input, show this alert
alert("Must enter an item name!");
}
});
无论何时添加新项目,新的点击处理程序都会绑定到所有项目。这意味着页面上存在的项目可能会得到两个或更多重复的处理程序。如果两个处理程序绑定到一个项目,第一个将 toggleClass
打开 "checked" class,第二个将立即关闭 class。
要使用事件委托,我建议只绑定一次处理程序,并将它们绑定到页面上始终存在的祖先。
例如:
// Bind "check" and "delete" handlers to the ".shopping-list" ancestor.
$(".shopping-list").on("click", ".shopping-item-toggle span", function() {
$(this).closest("li").find(".shopping-item").toggleClass("shopping-item__checked");
});
$(".shopping-list").on("click", '.shopping-item-delete', function() {
$(this).parent().parent().remove();
});
// Create a variable called buttons to add the 2 buttons in function below
let buttons = "<div class='shopping-item-controls'><button class='shopping-item-toggle'>\
<span class='button-label'>check</span></button>\
<button class='shopping-item-delete'><span class='button-label'>delete</span></button>\
</div>";
//Add new Item to List
$("#js-shopping-list-form").submit(function(event) {
event.preventDefault();
let item = $("#shopping-list-entry").val();
if (item != "") { // If the input has text in it, add the new item
$(".shopping-list").append("<li>" + "<span class='shopping-item'>" + item + "</span>" + buttons + "</li>");
} else { //if NO text is in the input, show this alert
alert("Must enter an item name!");
}
});
* {
box-sizing: border-box;
}
body {
font-family: 'Roboto', sans-serif;
}
button,
input[type="text"] {
padding: 5px;
}
button:hover {
cursor: pointer;
}
#shopping-list-item {
width: 250px;
}
.container {
max-width: 600px;
margin: 0 auto;
}
.shopping-list {
list-style: none;
padding-left: 0;
}
.shopping-list>li {
margin-bottom: 20px;
border: 1px solid grey;
padding: 20px;
}
.shopping-item {
display: block;
color: grey;
font-style: italic;
font-size: 20px;
margin-bottom: 15px;
}
.shopping-item__checked {
text-decoration: line-through;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="container">
<h1>Shopping List</h1>
<form id="js-shopping-list-form">
<label for="shopping-list-entry">Add an item</label>
<input type="text" name="shopping-list-entry" id="shopping-list-entry" placeholder="e.g., broccoli">
<button type="submit">Add item</button>
</form>
<ul class="shopping-list">
<li>
<span class="shopping-item">apples</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">oranges</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item shopping-item__checked">milk</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">bread</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
</ul>
</div>
下面是添加新项目后如何触发多个处理程序的演示:
//Make the Check Button functional
function checkButton() {
$(".shopping-item-toggle").on("click", "span", function() {
let $item = $(this).closest("li").find(".shopping-item");
console.log('Check Handler ' + ($item.hasClass('shopping-item__checked') ? 'OFF' : 'ON'));
$item.toggleClass("shopping-item__checked");
})
};
checkButton();
//Make the Delete Button functional
function delButton() {
$(".shopping-item-delete").on("click", function() {
console.log('Delete Handler');
$(this).parent().parent().remove();
})
};
delButton();
//Create a variable called buttons to add the 2 buttons in function below
let buttons = "<div class='shopping-item-controls'><button class='shopping-item-toggle'>\
<span class='button-label'>check</span></button>\
<button class='shopping-item-delete'><span class='button-label'>delete</span></button></div>";
//Add new Item to List
$("#js-shopping-list-form").submit(function(e) {
event.preventDefault();
let item = $("#shopping-list-entry").val();
if (item != "") { //As long as the input has text in it, run the function below
$(".shopping-list").append("<li>" + "<span class='shopping-item'>" + item + "</span>" + buttons + "</li>");
checkButton(); //Make the check button functional
delButton(); //Make the delete button functional
} else { //if NO text is in the input, show this alert
alert("Must enter an item name!");
}
});
* {
box-sizing: border-box;
}
body {
font-family: 'Roboto', sans-serif;
}
button,
input[type="text"] {
padding: 5px;
}
button:hover {
cursor: pointer;
}
#shopping-list-item {
width: 250px;
}
.container {
max-width: 600px;
margin: 0 auto;
}
.shopping-list {
list-style: none;
padding-left: 0;
}
.shopping-list>li {
margin-bottom: 20px;
border: 1px solid grey;
padding: 20px;
}
.shopping-item {
display: block;
color: grey;
font-style: italic;
font-size: 20px;
margin-bottom: 15px;
}
.shopping-item__checked {
text-decoration: line-through;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="container">
<h1>Shopping List</h1>
<form id="js-shopping-list-form">
<label for="shopping-list-entry">Add an item</label>
<input type="text" name="shopping-list-entry" id="shopping-list-entry" placeholder="e.g., broccoli">
<button type="submit">Add item</button>
</form>
<ul class="shopping-list">
<li>
<span class="shopping-item">apples</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">oranges</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item shopping-item__checked">milk</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
<li>
<span class="shopping-item">bread</span>
<div class="shopping-item-controls">
<button class="shopping-item-toggle"><span class="button-label">check</span></button>
<button class="shopping-item-delete"><span class="button-label">delete</span></button>
</div>
</li>
</ul>
</div>