如何在javascript中捕获双键按？

Question

我希望能够捕获双键按下(例如Char T)以进行一些特殊处理.我希望按键发生得足够快,不能被解释为两次单独按下,就像双击.任何想法我怎么能实现这一目标？

Answer 1

当击中键时,记下时间.然后将它与您上次敲击键时记录的时间进行比较.

如果差异在您的阈值范围内,请将其视为双倍.否则,不要.粗略的例子:

var delta = 500;
var lastKeypressTime = 0;
function KeyHandler(event)
{
   if ( String.fromCharCode(event.charCode).toUpperCase()) == 'T' )
   {
      var thisKeypressTime = new Date();
      if ( thisKeypressTime - lastKeypressTime <= delta )
      {
        doDoubleKeypress();
        // optional - if we'd rather not detect a triple-press
        // as a second double-press, reset the timestamp
        thisKeypressTime = 0;
      }
      lastKeypressTime = thisKeypressTime;
   }
}

Answer 2

有一个变量(可能first_press),当keypress事件发生时你设置为true,并启动一个计时器,它会在一段时间后将变量重置为false(无论你希望他们按键的速度多快).

在你的按键事件中,如果该变量为真,那么你有一个双按.

例:

var first_press = false;
function key_press() {
    if(first_press) {
        // they have already clicked once, we have a double
        do_double_press();
        first_press = false;
    } else {
        // this is their first key press
        first_press = true;

        // if they don't click again in half a second, reset
        window.setTimeout(function() { first_press = false; }, 500);
    }
}