How to trap double key press in javascript?
When the key(s) are hit, make a note of the time. Then compare it with the time you noted the last time they key(s) were hit.
If the difference is within your threshold, consider it a double. Otherwise, don't. Rough example:
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;
}
}
Have a variable (perhaps first_press
) that you set to true when a keypress event happens, and start a timer that will reset the variable to false after a set amount of time (however fast you want them to press the keys).
In your keypress event, if that variable is true then you have a double press.
Example:
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);
}
}