如何获取有关按下哪个键多长时间的信息？

发布于 2024-11-17 02:22:22 字数 345 浏览 3 评论 0原文

想象一下这段代码：

if (navigator.appName == "Opera")
    document.onkeypress = function (e) { console.log(e.keyCode); };
else 
    document.onkeydown = function (e) { console.log(e.keyCode); };

我想它的作用是非常明显的。问题是，如果你长时间持有密钥，它就会被注册很多次。在我的应用程序中，这是一个问题，因为它使我的应用程序执行大量不必要的计算。是否有可能以某种方式仅获得一次按键，但包含按键持续时间的信息？

原文

Imagine this code:

if (navigator.appName == "Opera")
    document.onkeypress = function (e) { console.log(e.keyCode); };
else 
    document.onkeydown = function (e) { console.log(e.keyCode); };

What it does is pretty obvious, I guess. The problem is, if you hold the key for a long period of time, it will be registered a lot of times. In my app, this is a problem because it makes my app do a lot of unnecessary computing. Is it possible to somehow only get a keypress once, but with info on how long the key was held?

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安稳善良 2024-11-24 02:22:22

在这里：

var pressed = {};

window.onkeydown = function(e) {
    if ( pressed[e.which] ) return;
    pressed[e.which] = e.timeStamp;
};

window.onkeyup = function(e) {
    if ( !pressed[e.which] ) return;
    var duration = ( e.timeStamp - pressed[e.which] ) / 1000;
    // Key "e.which" was pressed for "duration" seconds
    pressed[e.which] = 0;
};

现场演示： http://jsfiddle.net/EeXVX/ 1/show/

（删除 URL 的“show/”部分以查看演示代码）

因此，您拥有 pressed 对象，该对象监视当前按下的键以及按下的键他们当时在什么时间点按下。

在 keyup 处理程序中，您可以确定是否按下了按键，如果是，则通过减去 keyup/keydown 事件的时间戳来计算持续时间。

Here you go:

var pressed = {};

window.onkeydown = function(e) {
    if ( pressed[e.which] ) return;
    pressed[e.which] = e.timeStamp;
};

window.onkeyup = function(e) {
    if ( !pressed[e.which] ) return;
    var duration = ( e.timeStamp - pressed[e.which] ) / 1000;
    // Key "e.which" was pressed for "duration" seconds
    pressed[e.which] = 0;
};

Live demo: http://jsfiddle.net/EeXVX/1/show/

(remove the "show/" part of the URL to view the code for the demo)

So you have the pressed object which monitors which keys are currently being pressed and at what point (in time) they have been pressed.

Inside the keyup handler, you determine if the key was being pressed, and if so, calculate the duration by subtracting the time-stamps of the keyup/keydown events.

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