define()
方法在
CustomElementRegistry
interface defines a new custom element.
There are two types of custom elements you can create:
customElements.define(name, constructor, options);
Name for the new custom element. Note that custom element names must contain a hyphen.
Constructor for the new custom element.
extends
: String specifying the name of a built-in element to extend. Used to create a
customized built-in element
.
Void.
| 异常 | 描述 |
|---|---|
NotSupportedError
|
CustomElementRegistry
already contains an entry with the same name or the same constructor (or is otherwise already defined), or
extends
is specified and it is a
valid custom element name
，或
extends
is specified but the element it is trying to extend is an unknown element.
|
SyntaxError
|
The provided name is not a valid custom element name . |
TypeError
|
The referenced constructor is not a constructor. |
注意
: You'll often get
NotSupportedError
s thrown that seem like
define()
is failing, but instead it is likely a problem with
Element.attachShadow()
.
The following code is taken from our popup-info-box-web-component example ( see it live also ).
// Create a class for the element
class PopUpInfo extends HTMLElement {
constructor() {
// Always call super first in constructor
super();
// Create a shadow root
var shadow = this.attachShadow({mode: 'open'});
// Create spans
var wrapper = document.createElement('span');
wrapper.setAttribute('class','wrapper');
var icon = document.createElement('span');
icon.setAttribute('class','icon');
icon.setAttribute('tabindex', 0);
var info = document.createElement('span');
info.setAttribute('class','info');
// Take attribute content and put it inside the info span
var text = this.getAttribute('text');
info.textContent = text;
// Insert icon
var imgUrl;
if(this.hasAttribute('img')) {
imgUrl = this.getAttribute('img');
} else {
imgUrl = 'img/default.png';
}
var img = document.createElement('img');
img.src = imgUrl;
icon.appendChild(img);
// Create some CSS to apply to the shadow dom
var style = document.createElement('style');
style.textContent = '.wrapper {' +
'position: relative;' +
'}' +
'.info {' +
'font-size: 0.8rem;' +
'width: 200px;' +
'display: inline-block;' +
'border: 1px solid black;' +
'padding: 10px;' +
'background: white;' +
'border-radius: 10px;' +
'opacity: 0;' +
'transition: 0.6s all;' +
'position: absolute;' +
'bottom: 20px;' +
'left: 10px;' +
'z-index: 3;' +
'}' +
'img {' +
'width: 1.2rem' +
'}' +
'.icon:hover + .info, .icon:focus + .info {' +
'opacity: 1;' +
'}';
// attach the created elements to the shadow dom
shadow.appendChild(style);
shadow.appendChild(wrapper);
wrapper.appendChild(icon);
wrapper.appendChild(info);
}
}
// Define the new element
customElements.define('popup-info', PopUpInfo);
<popup-info img="img/alt.png" text="Your card validation code (CVC) is an extra
security feature — it is the last 3 or 4
numbers on the back of your card.">
注意
: Constructors for autonomous custom elements must extend
HTMLElement
.
The following code is taken from our word-count-web-component example ( see it live also ).
// Create a class for the element
class WordCount extends HTMLParagraphElement {
constructor() {
// Always call super first in constructor
super();
// count words in element's parent element
var wcParent = this.parentNode;
function countWords(node){
var text = node.innerText || node.textContent
return text.split(/\s+/g).length;
}
var count = 'Words: ' + countWords(wcParent);
// Create a shadow root
var shadow = this.attachShadow({mode: 'open'});
// Create text node and add word count to it
var text = document.createElement('span');
text.textContent = count;
// Append it to the shadow root
shadow.appendChild(text);
// Update count when element content changes
setInterval(function() {
var count = 'Words: ' + countWords(wcParent);
text.textContent = count;
}, 200)
}
}
// Define the new element
customElements.define('word-count', WordCount, { extends: 'p' });
<p is="word-count"></p>
| 规范 | 状态 | 注释 |
|---|---|---|
|
HTML 实时标准
The definition of 'customElements.define()' in that specification. |
实时标准 | 初始定义。 |
| 桌面 | 移动 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
define
|
Chrome
66
注意事项
|
Edge
79
注意事项
|
Firefox
63
|
IE 不支持 No |
Opera
53
注意事项
|
Safari
10.1
注意事项
|
WebView Android
66
注意事项
|
Chrome Android
66
注意事项
|
Firefox Android
63
|
Opera Android
47
注意事项
|
Safari iOS
10.3
注意事项
|
Samsung Internet Android
9.0
注意事项
|
完整支持
不支持
实验。期望将来行为有所改变。
见实现注意事项。
用户必须明确启用此特征。
CustomElementRegistry
define()
get()
upgrade()
whenDefined()