CustomElementRegistry.define()
Baseline
Widely available
*
This feature is well established and works across many devices and browser versions. It’s been available across browsers since 2020年1月.
* Some parts of this feature may have varying levels of support.
CustomElementRegistry接口的 define() 方法定义了一个自定义元素。
你可以创建两种类型的自定义元素：
- 自主定制元素：独立元素; 它们不会从内置 HTML 元素继承。
- 自定义内置元素：这些元素继承自 - 并扩展 - 内置 HTML 元素
语法
js
define(name, constructor)
define(name, constructor, options)
参数
- name
-
自定义元素名。
- constructor
-
自定义元素构造器。
- options 可选
-
控制元素如何定义。目前有一个选项支持：
extends. 指定继承的已创建的元素。被用于创建自定义元素。
返回值
空
示例
自主定制元素
以下代码取自我们的 popup-info-box-web-component 示例（查看实时运行版本）。
js
// 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);
html
<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."></popup-info>
备注：自主自定义元素的构造函数必须扩展HTMLElement。
自定义内置元素
以下代码取自我们的 word-count-web-component 实例（查看实例效果）。
js
// 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" });
html
<p is="word-count"></p>
规范
| Specification |
|---|
| HTML # dom-customelementregistry-define-dev |
浏览器兼容性
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