CODEWITHSUNDEEP
jquerykeydown
MarksCode
MarksCode

Reputation: 8584

Keydown stopping

I'm using an object to record what arrow keys are being pressed at an instance. While holding down left if I then also start holding down right, then stop holding down left my keydown function still runs, but if I do the same setup but stop holding down right instead, the function stops.

Here's the functions:

var keys = {};

$(document).keydown(function(e){
    keys[e.which] = true;
    console.log('h');
    moveBall();

});

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

function moveBall(){
    var vals = [];
    var ball = $("#ball1");
    var up = false;
    var down = false;
    var left = false;
    var right = false;
    for( var key in keys ) {
        if ( keys.hasOwnProperty(key) ) {
            vals.push(key);
        }
    }
    if ($.inArray("39", vals)> -1) right = true; // Right
    if ($.inArray("37", vals)> -1) left = true;
    if ($.inArray("38", vals)> -1) up = true;
    if ($.inArray("40", vals)> -1) down = true;


}

Can someone please explain why the ordering of when I stop pressing keys changes whether the keydown function still runs?

Upvotes: 2

Views: 94

Answers (1)

Roboroads
Roboroads

Reputation: 1709

So, you are trying to loop "moveBall" and so actions depending om which key is pressed.

I'm going to change your logic a little bit.

//Global object for what keys are active right now.

var keysBeingPressed = {
    right: false,
    left: false,
    up: false,
    down: false
};

$(document).keydown(function(e){
    // Set the right direction = true
    if (e.which == "39") keysBeingPressed.right = true;
    if (e.which == "37") keysBeingPressed.left = true;
    if (e.which == "38") keysBeingPressed.up = true;
    if (e.which == "40") keysBeingPressed.down = true;
});

$(document).keyup(function(e){
    // Set the right direction = false
    if (e.which == "39") keysBeingPressed.right = false;
    if (e.which == "37") keysBeingPressed.left = false;
    if (e.which == "38") keysBeingPressed.up = false;
    if (e.which == "40") keysBeingPressed.down = false;
});



function moveBall(){
    var ball = $("#ball1");

    // Going left is decreasing X, right is increasing X.
    // Going up is decreasing Y, down increases Y.
    // So, up+left, is diagonal, you move x and y both..
    var movement = {
        x: 0,
        y: 0
    }

    if(keysBeingPressed.right) movement.x++;
    if(keysBeingPressed.left) movement.x--;  //If left+right; x = 1 - 1 = 0 so no movement.
    if(keysBeingPressed.up) movement.y--;
    if(keysBeingPressed.down) movement.y++;

    // add your movement in x/y to top/left
    ball.css({
        top: "+="+movement.y,  //+= adds the value
        left: "+="+movement.x
    });
}

// Loop this function, you want it to run every "animation frame"
setInterval(function(){
    moveBall();
}, 10);

I did add code to move the ball.

Upvotes: 3

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