How can I catch 2+ key presses at once?

问题:

Well lately i got interested in creating JS games. (not an area i have experience with but it interests me).

i know there are several gaming engines for JS out there but i dont really want to create a game. rather i am curious on how things work / how can i create one.

I have several questions:

1. Anyone with suggestions on where can I read about it? Prerequisite (what knowledge is needed).

2. I tried making a small game of something walking in a rectangular. By binding keyup to the window and checking the event.which to get the key that was pressed. I realized that if i clicked on 2 buttons same time only 1 of them is being registered. how can i overcome that?

   $(window).keyup(function(event){
        globalEvent = event.which;
   
   });
   

回答1:

To directly answer your second question.

Here is one way:

var keyPressed = {};

$(window).keydown(function(e) {
    keyPressed[e.which] = true;
}).keyup(function(e) {
    keyPressed[e.which] = false;
});

Now you can use keyPressed whenever you want to determine if a key is down:

// wherever
var key1 = 65, key2 = 66; // A and B
if (keyPressed[key1] && keyPressed[key2]) {
    // A and B are both being pressed.
}

回答2:

In order to detect multiple keys being held down, use the keydown and keyup events.

var keys = {};

$(document).keydown(function (e) {
    keys[e.which] = true;
});

$(document).keyup(function (e) {
    delete keys[e.which];
});