Develop Reference

js - trigger generic function on space bar press anywhere on document

I have a colour guessing game with six different colour squares and an rgb code at the top of the page. The game works and the game resets via function - resetUI() - when a reset button on the page is clicked.
However, I want to trigger the resetUI function whenever the space bar is pressed. I have the following code, it doesn't throw any errors but it also doesn't work:
var body = document.querySelector("body");
body.addEventListener("keydown",function(){
if(this.key === " "){
resetUI();
}
});
I am fairly certain my use of "this" is wrong but I can't think of an alternative.
I have searched MDN and stackOverflow but I haven't seen a solution to this problem. Thanks.

key belongs to the event (which is passed into the event handler), not the body (which is what this refers to).
The next problem you will have is when you add an input or textarea to the page and anytime the user put a space into the input it will run your function.. You can check against the target to make sure the input isn't receiving the keystroke before you fire your function..
var body = document.querySelector("body");
body.addEventListener("keydown",function(e){
var isInput = ~["TEXTAREA", "INPUT"].indexOf(e.target.tagName);
if(e.key === " " && !isInput){
// resetUI();
console.log("u clicked spacebar, and it wasn't in an input");
}
});
<input />

You have lot of unnecessary code. And you should receive the event object from callback function to check against which key got pressed.
To check spacebar you shouldn't check against " " instead you have to check the keyCode of event.
document.body.onkeydown = function(e){
if(e.keyCode == 32){
console.log("space bar pressed");
resetUI();
}
}

Toggled boolean variable evaluated in conditional statement on click event

I am toggling the boolean variable "userTurn". There are two functions that set the value of "userTurn":
runGame(), which sets "userTurn" to true after the last sound in the current round is played.
buttonClick(), which should only be executed if "userTurn" is true. buttonClick sets "userTurn" to false after the user successfully copies the current pattern, or if the user makes a mistake.
I am evaluating the value of "userTurn" in a conditional statement that is inside of a click event.
$(".quarter").on('click', function(){
if( userTurn===true && isOn===true){
var color = $(this).attr('id');
clearTimeout(buzz);
buttonClick(color);
}
})
After the user successfully copies the current pattern, or if the user makes a mistake, "userTurn" is set to false. The problem I am running into is, after "userTurn" is set to false, the code inside the conditional statement is still executing. The goal is for ".quarter" to only be clickable when "userTurn" is true. Why is the buttonClick() function still executing when ".quarter" is clicked even when "userTurn" is false??
Here are the two functions that set the value of "userTurn":
runGame():
function runGame(){
if(isOn===true){
userTurn = false;
count();
playPattern(order, index);
if(index===counter-1&&userTurn===false){
userTurn=true;
clearInterval(play);
buzz = setTimeout(buzzer, 10000);
}else{
index++;
}
} else {
clearInterval(play);
clearTimeout(buzz);
}
}
2.buttonClick():
function buttonClick(color){
var yellowSound = document.getElementById("horseSound");
var redSound = document.getElementById("endFx");
var greenSound = document.getElementById("westernRicochet");
var blueSound = document.getElementById("robotBlip");
$("#red").mousedown(function(){
$("#red").css("background-color", "#ff4d4d");
redSound.play();
});
$("#red").mouseup(function(){
$("#red").css("background-color", "#ff0000");
redSound.pause();
});
$("#blue").mousedown(function(){
$("#blue").css("background-color", "#0000e6");
blueSound.play();
});
$("#blue").mouseup(function(){
$("#blue").css("background-color", "#000099");
blueSound.pause();
});
$("#green").mousedown(function(){
$("#green").css("background-color", "#00e600");
greenSound.play();
});
$("#green").mouseup(function(){
$("#green").css("background-color", "#009900");
greenSound.pause();
});
$("#yellow").mousedown(function(){
$("#yellow").css("background-color", "#ffff4d");
yellowSound.play();
});
$("#yellow").mouseup(function(){
$("#yellow").css("background-color", "#ffff00");
yellowSound.pause();
});
if(color===order[compareIndex]){
userPattern.push(color);
console.log(userPattern, "match");
buzz = setTimeout(buzzer, 10000);
compareIndex++;
if(userPattern.length===counter){
userTurn=false;
compareIndex=0;
index=0;
counter++;
count();
userPattern.length=0;
play = setInterval(runGame, 2000);
clearTimeout(buzz);
}
} else {
userTurn=false;
console.log('don\'t match');
clearTimeout(buzz);
index=0;
compareIndex = 0;
userPattern.length=0;
buzz = setTimeout(buzzer, 1);
}
}
TURN DOWN YOUR VOLUME BEFORE GOING TO THE CODEPEN!!
Here is a link to the codepen.
To start the game click "On Off" and then click "start". The timing is slow so you have to wait for the pattern to play, then click the buttons in the same order as they were played. The problem is seen after the first sound is played. From that point on any click the user makes will play the sound and light up the button, even when the game is playing the pattern and "userTurn" is false. Also be warned, this is still a work in progress, there are a couple of other bugs I'm working on, for example the the first turn the user makes will not light up or play the sound, but the selection is pushed into the correct array and the game will proceed properly based on your selection. I know this is a lot of info but I'm stuck on this so any feed back will be very appreciated. Thanks!

You're using buttonClick to handle clicking the buttons, but inside buttonClick you're setting mouseup and mousedown event listeners for each button as well. Since the individual buttons have their own mouseup and mousedown listeners, the events will happen whether or not buttonClick is called again.
You would have to check if userTurn is true inside of each of those event handlers as well to prevent them from triggering. Also, it would better to set these outside of buttonClick so you won't be adding new listeners every time buttonClick gets called.

Shortcut keys for Javascript game GUI

I've been making a simple javascript based OOP text game that uses string replacement and variable adjustments tied to button .onclick events. I've been asked to add hotkeys for easier access, and I've been struggling with how to do it.
First I tried using the JSQuery hotkeys script and the .bind command, but that seemed like it would be very time consuming as I'd have to recode every .onclick as a hotkey, and even with unbind, it was firing off every event tied to the key on the script.
I feel like the best way to do would be if I could code the keys to the gui, i.e. if when you pressed "1", it activated the .onclick of button 1, that way the hotkey would be static (except when the button is disabled), but I've no idea how to do that. I've just been using html buttons, (i.e. input type="button" value="" disabled="disabled" id="button1"), I suspect I'd need something more sophisticated?
Thanks in advance for any help, google has been useless.
[EDIT - General description of code]
The way the game works is very simple, via the calling of functions as new events with different text/buttons (and different onclick events tied to those buttons). As an example, the start screen code is:
function startScreen() {
$(document).ready(function () {
$('#text').html("Game title and info");
$('#button1').val("Start Game");
$('#button1').attr("disabled", false);
$("#button1").one("click", function () {
textClear();
buttonClear();
nameScreen();
});
$("#button2").val("Load Game");
$('#button2').attr("disabled", false);
$("#button2").one("click", function () {
textClear();
buttonClear();
loadData();
});
$("#button6").val("Settings");
$('#button6').attr("disabled", false);
$("#button6").one("click", function () {
textClear();
buttonClear();
settingsScreen();
});
});
}
Since the code executed by button one changes between functions, what the hotkey does as well, which was my problem with using the JQuery library code.

When a key is pressed then the event onkeypress is fired. This event provides some values like:
keyCode
charCode
which
So you could do something like:
window.onkeypress = function (event) {
// the keyCode value for the key 1 is 49, for the key 2 is 50
if (event.keyCode == 49) {
// execute the same code as clicking the button 1
console.log("The key 1 was pressed.");
} else if (event.keyCode == 50) {
// execute the same code as clicking the button 2
console.log("The key 2 was pressed.");
}
};
Now, when a user visits your website he could press the keys 1 or 2 on the keyboard and fire the same logic as clicking the buttons "1" and "2" (being something like <input id="button1">) with the left mouse taste.
If you have really a lot of hotkeys then this would be also tedious to type, but without knowing your code I can hardly give you a complete solution. I hope my answer can give you some idea how to proceed further.
EDIT:
Further reading on the topic:
http://unixpapa.com/js/key.html

Changing my HTML5 game controls to mouse/touch

So I have my controls set up as space bar to jump but I want my HTML5 game to work everywhere so I need to change it to mouse/touch. Mouse/touch doesnt have a keycode so whats the most optimal way to do it for this code? Do I need to do mouse and touch separately?
if (KEY_STATUS.space && player.dy === 0 && !player.isJumping) {
player.isJumping = true;
player.dy = player.jumpDy;
jumpCounter = 12;
assetLoader.sounds.jump.play();
}
// jump higher if the space bar is continually pressed
if (KEY_STATUS.space && jumpCounter) {
player.dy = player.jumpDy;
}

You are talking about touch events in JavaScript. You will have to add an event listener and catch if the user touches screen. Here you can find a well documented tutorial in how to use it on both touchscreen and mouse.
Check out the first answer, you will have to do it like that. You will have to add an event listener on the canvas itself, like the guy did it on myDiv.
Here is an example I wrote (don't mind me being weird, please):
<div id="fakeCanvas">
Click or touch me!
</div>
<script type="text/javascript">
var fakeCanvas = document.getElementById('fakeCanvas');
function methodToInvokeForClick() {
alert('I have been clicked!');
}
function methodToInvokeForTouch() {
alert('I have been touched!');
}
fakeCanvas.addEventListener("click", methodToInvokeForClick, false);
fakeCanvas.addEventListener("touchstart", methodToInvokeForTouch, false);
</script>
I think you can take it over from now. What I did to the fakeCanvas div, you will have to do the same to your canvas by giving it an id etc. Good luck!

JS: How to prevent the default action on images in browsers?

In IE, for example, when you press the left button on an image and keeping it pressed try to move the mouse, the drag n' drop action is taking place; how could I prevent this default action so that doing that way nothing will happen. I am building an image cropper, so you should understand why I need that. I am not much interested in knowing how to do so with help of jQuery or the like. As I study JavaScript, I prefer coding in plain-vanilla JS. It is important for me to learn how to make it cross-browser if there are any differences for such a thing.

Just like August's, but plain JS:
var imgs = document.getElementById("my_container")
.getElementsByTagName("img");
for (var i = 0; i < imgs.length; i++) {
imgs[i].onmousedown = function () {
return false;
};
}
If you want to do it 'new-style', google for 'addEventListener()' (all browsers but...) and 'attachEvent()' (...IE) methods.

Here's one in jQuery:
$("#my_container img").mousedown(function () {
return false;
});
http://www.google.com/search?q=cross+browser+event+hooking will probably teach you everything you need to know about cross browser event hooking. I don't know how to hook events without a framework, because that's an edge case IMHO. In The Real World (tm), you'll always use a framework.
The core here is that you have to stop the mousedown event from running. This will make drag and drop impossible, if you hook the event on text you won't be able to select that text, and so on.

If you're building an image cropper, you're going to put some kind of overlay on the image, probably a relatively or absolutely positioned div, inside of which you will "draw" a rectangle when the user clicks, holds and drags. This will make it impossible for the user to drag the image itself, so no fix for that is needed.
Even if you do not use an overlay, you are still going to hook the mousedown event - there is no other way to implement a JS cropper as far as I know. Hooking that event will by itself be enough to prevent the browser from initiating a drag and drop action.

I'm using code similar to the following to prevent dragging, which has the advantage of targetting actual drag-related events rather than the generic mousedown (which could conceivably have side-effects). Works in all the mainstream browsers except Opera.
function cancellingEventHandler(evt) {
evt = evt || window.event;
if (evt.preventDefault) {
evt.preventDefault();
} else if (typeof evt.returnValue !== "undefined") {
evt.returnValue = false;
}
return false;
}
function disableDragging(node) {
node.ondragstart = cancellingEventHandler;
node.ondraggesture = cancellingEventHandler;
}
disableDragging( document.getElementById("anImage") );