keydown combination

Question

how do i check if a combination of keys are pressed with jquery?

lets say i want to fire up an alert only when the up and down arrow keys are pressed at the same time.

right now im just using:

switch (event.which) {
    case 40:
        alert('down');
        break;
    case 38:
        alert('up');
        break;
    case 37:
        alert('left');
        break;
    case 39:
        alert('right');
        break;
}

Answer 1

Set flags. When one key goes down, if it's a certain keyCode, set your flag myKeyIsDown = true. When it comes up, set the flag back to false. When your second key goes down, if it is of a certain keyCode and your myKeyIsDown flag is true, you've got two keys down.

Answer 2

You could try using a plugin like this (demo)

Answer 3

One suggestion in followup to another answer, you might want to stop the cascade of the event on the second key press, which could be done similar to this: (put your logic in of course)

/* handle special key press */ 
function checkCptKey(e) 
{ 
    var shouldBubble = true; 
    switch (e.keyCode) 
    { 
        // user pressed the Tab                                                                                                                                         
        case 9: 
            { 
                $(".someSelect").toggleClass("classSelectVisible"); 
                shouldBubble = false; 
                break; 
            }; 
            // user pressed the Enter     
        case 13: 
            { 
                $(".someSelect").toggleClass("classSelectVisible"); 
                break; 
            }; 
            // user pressed the ESC 
        case 27: 
            { 
                $(".someSelect").toggleClass("classSelectVisible"); 
                break; 
            }; 
    }; 
    /* this propogates the jQuery event if true */ 
    return shouldBubble; 
}; 

/* user pressed special keys while in Selector */ 
$(".mySelect").keydown(function(e) 
{ 
    return checkCptKey(e); 
});