GlobalEventHandlers.onpointerdown

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GlobalEventHandlers event handler onpointerdown is used to specify the event handler for the pointerdown event, which is fired when the pointing device is initially pressed. This event can be sent to Window , Document ，和 元素 对象。

This is functionally equivalent to the mousedown event when generated due to user activity with a mouse or mouse-compatible device. If the pointerdown event isn't canceled through a call to preventDefault() , most user agents will fire a mousedown event, so that sites not using pointer events will work.

还可以使用 addEventListener() to add a listener for pointerdown 事件。

句法

target.onpointerdown = downHandler;
var downHandler = target.onpointerdown;

值

A 函数 to handle the pointerdown 事件为 target 元素 , Document ，或 Window . It receives as input the PointerEvent describing the pointerdown 事件。

范例

This example demonstrates how to watch for and act upon pointerdown events using onpointerdown . You could also use addEventListener() , of course.

JavaScript

First, let's look at the JavaScript code that handles the pointerdown 事件。

var targetBox = document.getElementById("target");
targetBox.onpointerdown = handleDown;
function handleDown(evt) {
  var action;
  switch(evt.pointerType) {
    case "mouse":
      action = "clicking";
      break;
    case "pen":
      action = "tapping";
      break;
    case "touch":
      action = "touching";
      break;
    默认：
      action = "interacting with";
      break;
  }
  targetBox.innerHTML = "<strong>Thanks for " + action + " me!</strong>";
  evt.preventDefault();
}

This simply uses onpointerdown to establish the function handleDown() as the event handler for pointer down events.

handleDown() function, in turn, looks at the value of pointerType to determine what kind of pointing device was used, then uses that information to customize a string to replace the contents of the target box.

Then the event's preventDefault() method is called to ensure that the mousedown event isn't triggered, potentially causing events to be handled twice if we had a handler for those events in case Pointer Event support is missing.

We also have a handler for pointerup 事件：

targetBox.onpointerup = handleUp;
function handleUp(evt) {
  targetBox.innerHTML = "Tap me, click me, or touch me!";
  evt.preventDefault();
}

This code's job is to just restore the original text into the target box after the user's interaction with the element ends (for example, when they release the mouse button, or when they lift the stylus or finger from the screen).

In addition, the event's preventDefault() method is called to ensure that the mouseup event isn't triggered unnecessarily.

HTML

The HTML is extremely simple:

<div id="target">
  Tap me, click me, or touch me!
</div>

CSS

The CSS simply sets up the appearance of the target, and doesn't affect its functionality at all.

#target {
  width: 400px;
  height: 30px;
  text-align: center;
  font: 16px "Open Sans", "Helvetica", sans-serif;
  color: white;
  background-color: blue;
  border: 2px solid darkblue;
  cursor: pointer;
  user-select: none;
  -moz-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
}

结果

The resulting output is shown below. Try tapping, clicking, or touching the box and see what happens. For full effect, try it with a variety of pointer types.

规范

规范	状态	注释
指针事件 – 2 级 The definition of 'onpointerdown' in that specification.	推荐	Non-stable version
指针事件 The definition of 'onpointerdown' in that specification.	过时	初始定义

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`onpointerdown`	Chrome 55	Edge 12 12 不支持 12 — 79 Alternate Name Alternate Name Uses the non-standard name: `onmspointerdown`	Firefox 59 59 Disabled ). To change preferences in Firefox, visit	IE 11 11 10 Alternate Name Alternate Name Uses the non-standard name: `onmspointerdown`	Opera ?	Safari No	WebView Android 55	Chrome Android 55	Firefox Android 29	Opera Android ?	Safari iOS No	Samsung Internet Android 6.0

图例

完整支持
不支持
兼容性未知 ?
用户必须明确启用此特征。

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元数据

最后修改： Aug 12, 2020

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句法

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JavaScript

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CSS

结果

规范

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图例

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