为什么'keydown'事件就像'keypress'事件一样？ [英] Why 'keydown' event works like 'keypress' event?
问题描述
当我按住按钮时，下一个示例代码多次输出'keydown'消息。文档说只需按一下按钮即可发生一次keydown事件。因此，keydown事件的作用类似于下一个示例中的按键事件。
The next sample code outputs 'keydown' message many times while I hold a button down. The docs says that the keydown event happens once for one push of the button. So, the keydown event works like the keypress event in the next example.
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title></title>
<script type='text/javascript' src='jquery.js'></script>
<script type='text/javascript'>
function onLoad()
{
$( '#text' ).on( 'keydown', function() { console.info( 'keydown' ) } );
}
</script>
</head>
<body onload='onLoad()'>
<input type='text' id='text'>
</body>
</html>
我在Windows，Firefox 19.0.2和Google Chrome 25.0.1364.152上进行了测试。我还创建了一个小提琴（问题可以复制）。重现问题的JQuery版本：1.8.2,1.9.1。
I tested it on Windows, Firefox 19.0.2 and Google Chrome 25.0.1364.152. Also I created a fiddle (the problem can be reproduced). JQuery versions for which problem is reproduced: 1.8.2, 1.9.1.
更新。
我做了意识到这个问题：如何在JavaScript中避免自动重复的keydown事件？ 。
I did realize the problem: How can I avoid autorepeated keydown events in JavaScript?.
推荐答案
keydown按下键时发生事件，紧接着是keypress事件。然后在释放密钥时生成keyup事件。
The
keydownevent occurs when the key is pressed, followed immediately by thekeypressevent. Then thekeyupevent is generated when the key is released.
为了理解<$ c之间的区别$ c> keydown 和 keypress ，了解字符和键之间的区别很有用。 键是计算机键盘上的物理按钮，而字符是通过按下按钮键入的符号。理论上， keydown 和 keyup 事件表示按下或释放的键，而按键 event表示正在键入的字符。所有浏览器的理论实现都不相同。
In order to understand the difference between keydown and keypress, it is useful to understand the difference between a "character" and a "key". A "key" is a physical button on the computer's keyboard while a "character" is a symbol typed by pressing a button. In theory, the keydown and keyup events represent keys being pressed or released, while the keypress event represents a character being typed. The implementation of the theory is not same in all browsers.
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