I have a function which "types" out a header title as though it is being typed on the screen.
The typer only starts typing once a particular section of my site is "active" or is seen on the screen.
At present, it takes the outputID aka the area where this text will be typed into. There are two instances of this function being run, each with different outputIDs - I only want the function to run once per outputID.
This is how the function is initially called.
<h2 id="typer-get-in-touch" class="typer" data-text="Get in Toche^^^^^ Touch"></h2>
if(anchorLink == 'contact'){
var outputID = $("#typer-get-in-touch");
textTyping(outputID);
}else if(anchorLink == 'expertise'){
var outputID = $("#typer-expertise");
textTyping(outputID);
}
This is the textTyping function
function textTyping(outputID){
$(outputID).show();
var textString = $(outputID).data("text");
var textArray = textString.split("");
var texttypeing = setInterval(
function() {
typeOutText(outputID,textArray);
}, 170);
function typeOutText(outputID,textArray) {
if (textArray[0] == "^"){
outputID.text(function(index, text){
return text.replace(/(\s+)?.$/, '');
});
textArray.shift();
}else {
if (textArray.length > 0) {
outputID.append(textArray.shift());
} else {
clearTimeout(texttypeing);
}
}
}
}
My issue at present is that the function runs multiple types, and continues to type each time the original anchorLink trigger is achieved. The result is that is writes the title many times e.g:
Get In TouchGet In TouchGet In Touch
Each time the section is navigated to, the typing starts again.
How can I run this function only ONCE per outputID? So once the outputID has been used, the function can no longer run for that data?
JSFiddle of non-working example: https://jsfiddle.net/qLez8zeq/
JSFiddle of mplungjan's solution: https://jsfiddle.net/qLez8zeq/1/
Change
function textTyping(outputID){
$(outputID).show();
var textString = $(outputID).data("text");
to
function textTyping(outputID){
var textString = $(outputID).data("text");
if (textString=="") return;
$(outputID).data("text","");
$(outputID).show();
FIDDLE
What you need to do is to bind the event handler for each ID and then unbind it after it's been triggered the first time. Since you're already using jQuery, you can use the "one" method to do exactly this for each outputID:
$( "#typer-get-in-touch" ).one( "click", function() {
textTyping(outputID);
});
I suppose you could store your processed outputIds into an array and then check if the given outputId is present in the array before starting?
Define your array, check for the existence, if not found, do code example:
var processedIds = [];
function textTyping(outputID) {
var foundItem = false;
for (var i = 0; i < processedIds.length; i++)
{
if (processedIds[i] == outputID) {
foundItem = true;
break;
}
}
if (!foundItem) {
//the rest of your code goes here
}
}
You can add some check at the beginning of your function:
var called = {};
function textTyping(outputID) {
if (called[outputID]) {
return;
}
called[outputID] = true;
// your code
}
I'm trying to develop a JavaScript game engine and I've came across this problem:
When I press SPACE the character jumps.
When I press → the character moves right.
The problem is that when I'm pressing right and then press space, the character jumps and then stops moving.
I use the keydown function to get the key pressed. How can I check if there are multiple keys pressed at once?
Note: keyCode is now deprecated.
Multiple keystroke detection is easy if you understand the concept
The way I do it is like this:
var map = {}; // You could also use an array
onkeydown = onkeyup = function(e){
e = e || event; // to deal with IE
map[e.keyCode] = e.type == 'keydown';
/* insert conditional here */
}
This code is very simple: Since the computer only passes one keystroke at a time, an array is created to keep track of multiple keys. The array can then be used to check for one or more keys at once.
Just to explain, let's say you press A and B, each fires a keydown event that sets map[e.keyCode] to the value of e.type == keydown, which evaluates to either true or false. Now both map[65] and map[66] are set to true. When you let go of A, the keyup event fires, causing the same logic to determine the opposite result for map[65] (A), which is now false, but since map[66] (B) is still "down" (it hasn't triggered a keyup event), it remains true.
The map array, through both events, looks like this:
// keydown A
// keydown B
[
65:true,
66:true
]
// keyup A
// keydown B
[
65:false,
66:true
]
There are two things you can do now:
A) A Key logger (example) can be created as a reference for later when you want to quickly figure out one or more key codes. Assuming you have defined an html element and pointed to it with the variable element.
element.innerHTML = '';
var i, l = map.length;
for(i = 0; i < l; i ++){
if(map[i]){
element.innerHTML += '<hr>' + i;
}
}
Note: You can easily grab an element by its id attribute.
<div id="element"></div>
This creates an html element that can be easily referenced in javascript with element
alert(element); // [Object HTMLDivElement]
You don't even have to use document.getElementById() or $() to grab it. But for the sake of compatibility, use of jQuery's $() is more widely recommended.
Just make sure the script tag comes after the body of the HTML. Optimization tip: Most big-name websites put the script tag after the body tag for optimization. This is because the script tag blocks further elements from loading until its script is finished downloading. Putting it ahead of the content allows the content to load beforehand.
B (which is where your interest lies) You can check for one or more keys at a time where /*insert conditional here*/ was, take this example:
if(map[17] && map[16] && map[65]){ // CTRL+SHIFT+A
alert('Control Shift A');
}else if(map[17] && map[16] && map[66]){ // CTRL+SHIFT+B
alert('Control Shift B');
}else if(map[17] && map[16] && map[67]){ // CTRL+SHIFT+C
alert('Control Shift C');
}
Edit: That isn't the most readable snippet. Readability's important, so you could try something like this to make it easier on the eyes:
function test_key(selkey){
var alias = {
"ctrl": 17,
"shift": 16,
"A": 65,
/* ... */
};
return key[selkey] || key[alias[selkey]];
}
function test_keys(){
var keylist = arguments;
for(var i = 0; i < keylist.length; i++)
if(!test_key(keylist[i]))
return false;
return true;
}
Usage:
test_keys(13, 16, 65)
test_keys('ctrl', 'shift', 'A')
test_key(65)
test_key('A')
Is this better?
if(test_keys('ctrl', 'shift')){
if(test_key('A')){
alert('Control Shift A');
} else if(test_key('B')){
alert('Control Shift B');
} else if(test_key('C')){
alert('Control Shift C');
}
}
(end of edit)
This example checks for CtrlShiftA, CtrlShiftB, and CtrlShiftC
It's just as simple as that :)
Notes
Keeping Track of KeyCodes
As a general rule, it is good practice to document code, especially things like Key codes (like // CTRL+ENTER) so you can remember what they were.
You should also put the key codes in the same order as the documentation (CTRL+ENTER => map[17] && map[13], NOT map[13] && map[17]). This way you won't ever get confused when you need to go back and edit the code.
A gotcha with if-else chains
If checking for combos of differing amounts (like CtrlShiftAltEnter and CtrlEnter), put smaller combos after larger combos, or else the smaller combos will override the larger combos if they are similar enough. Example:
// Correct:
if(map[17] && map[16] && map[13]){ // CTRL+SHIFT+ENTER
alert('Whoa, mr. power user');
}else if(map[17] && map[13]){ // CTRL+ENTER
alert('You found me');
}else if(map[13]){ // ENTER
alert('You pressed Enter. You win the prize!')
}
// Incorrect:
if(map[17] && map[13]){ // CTRL+ENTER
alert('You found me');
}else if(map[17] && map[16] && map[13]){ // CTRL+SHIFT+ENTER
alert('Whoa, mr. power user');
}else if(map[13]){ // ENTER
alert('You pressed Enter. You win the prize!');
}
// What will go wrong: When trying to do CTRL+SHIFT+ENTER, it will
// detect CTRL+ENTER first, and override CTRL+SHIFT+ENTER.
// Removing the else's is not a proper solution, either
// as it will cause it to alert BOTH "Mr. Power user" AND "You Found Me"
Gotcha: "This key combo keeps activating even though I'm not pressing the keys"
When dealing with alerts or anything that takes focus from the main window, you might want to include map = [] to reset the array after the condition is done. This is because some things, like alert(), take the focus away from the main window and cause the 'keyup' event to not trigger. For example:
if(map[17] && map[13]){ // CTRL+ENTER
alert('Oh noes, a bug!');
}
// When you Press any key after executing this, it will alert again, even though you
// are clearly NOT pressing CTRL+ENTER
// The fix would look like this:
if(map[17] && map[13]){ // CTRL+ENTER
alert('Take that, bug!');
map = {};
}
// The bug no longer happens since the array is cleared
Gotcha: Browser Defaults
Here's an annoying thing I found, with the solution included:
Problem: Since the browser usually has default actions on key combos (like CtrlD activates the bookmark window, or CtrlShiftC activates skynote on maxthon), you might also want to add return false after map = [], so users of your site won't get frustrated when the "Duplicate File" function, being put on CtrlD, bookmarks the page instead.
if(map[17] && map[68]){ // CTRL+D
alert('The bookmark window didn\'t pop up!');
map = {};
return false;
}
Without return false, the Bookmark window would pop up, to the dismay of the user.
The return statement (new)
Okay, so you don't always want to exit the function at that point. That's why the event.preventDefault() function is there. What it does is set an internal flag that tells the interpreter to not allow the browser to run its default action. After that, execution of the function continues (whereas return will immediately exit the function).
Understand this distinction before you decide whether to use return false or e.preventDefault()
event.keyCode is deprecated
User SeanVieira pointed out in the comments that event.keyCode is deprecated.
There, he gave an excellent alternative: event.key, which returns a string representation of the key being pressed, like "a" for A, or "Shift" for Shift.
I went ahead and cooked up a tool for examining said strings.
element.onevent vs element.addEventListener
Handlers registered with addEventListener can be stacked, and are called in the order of registration, while setting .onevent directly is rather aggressive and overrides anything you previously had.
document.body.onkeydown = function(ev){
// do some stuff
ev.preventDefault(); // cancels default actions
return false; // cancels this function as well as default actions
}
document.body.addEventListener("keydown", function(ev){
// do some stuff
ev.preventDefault() // cancels default actions
return false; // cancels this function only
});
The .onevent property seems to override everything and the behavior of ev.preventDefault() and return false; can be rather unpredictable.
In either case, handlers registered via addEventlistener seem to be easier to write and reason about.
There is also attachEvent("onevent", callback) from Internet Explorer's non-standard implementation, but this is beyond deprecated and doesn't even pertain to JavaScript (it pertains to an esoteric language called JScript). It would be in your best interest to avoid polyglot code as much as possible.
A helper class
To address confusion/complaints, I've written a "class" that does this abstraction (pastebin link):
function Input(el){
var parent = el,
map = {},
intervals = {};
function ev_kdown(ev)
{
map[ev.key] = true;
ev.preventDefault();
return;
}
function ev_kup(ev)
{
map[ev.key] = false;
ev.preventDefault();
return;
}
function key_down(key)
{
return map[key];
}
function keys_down_array(array)
{
for(var i = 0; i < array.length; i++)
if(!key_down(array[i]))
return false;
return true;
}
function keys_down_arguments()
{
return keys_down_array(Array.from(arguments));
}
function clear()
{
map = {};
}
function watch_loop(keylist, callback)
{
return function(){
if(keys_down_array(keylist))
callback();
}
}
function watch(name, callback)
{
var keylist = Array.from(arguments).splice(2);
intervals[name] = setInterval(watch_loop(keylist, callback), 1000/24);
}
function unwatch(name)
{
clearInterval(intervals[name]);
delete intervals[name];
}
function detach()
{
parent.removeEventListener("keydown", ev_kdown);
parent.removeEventListener("keyup", ev_kup);
}
function attach()
{
parent.addEventListener("keydown", ev_kdown);
parent.addEventListener("keyup", ev_kup);
}
function Input()
{
attach();
return {
key_down: key_down,
keys_down: keys_down_arguments,
watch: watch,
unwatch: unwatch,
clear: clear,
detach: detach
};
}
return Input();
}
This class doesn't do everything and it won't handle every conceivable use case. I'm not a library guy. But for general interactive use it should be fine.
To use this class, create an instance and point it to the element you want to associate keyboard input with:
var input_txt = Input(document.getElementById("txt"));
input_txt.watch("print_5", function(){
txt.value += "FIVE ";
}, "Control", "5");
What this will do is attach a new input listener to the element with #txt (let's assume it's a textarea), and set a watchpoint for the key combo Ctrl+5. When both Ctrl and 5 are down, the callback function you passed in (in this case, a function that adds "FIVE " to the textarea) will be called. The callback is associated with the name print_5, so to remove it, you simply use:
input_txt.unwatch("print_5");
To detach input_txt from the txt element:
input_txt.detach();
This way, garbage collection can pick up the object (input_txt), should it be thrown away, and you won't have an old zombie event listener left over.
For thoroughness, here is a quick reference to the class's API, presented in C/Java style so you know what they return and what arguments they expect.
Boolean key_down (String key);
Returns true if key is down, false otherwise.
Boolean keys_down (String key1, String key2, ...);
Returns true if all keys key1 .. keyN are down, false otherwise.
void watch (String name, Function callback, String key1, String key2, ...);
Creates a "watchpoint" such that pressing all of keyN will trigger the callback
void unwatch (String name);
Removes said watchpoint via its name
void clear (void);
Wipes the "keys down" cache. Equivalent to map = {} above
void detach (void);
Detaches the ev_kdown and ev_kup listeners from the parent element, making it possible to safely get rid of the instance
Update 2017-12-02 In response to a request to publish this to github, I have created a gist.
Update 2018-07-21 I've been playing with declarative style programming for a while, and this way is now my personal favorite: fiddle, pastebin
Generally, it'll work with the cases you would realistically want (ctrl, alt, shift), but if you need to hit, say, a+w at the same time, it wouldn't be too difficult to "combine" the approaches into a multi-key-lookup.
I hope this thoroughly explained answer mini-blog was helpful :)
document.onkeydown = keydown;
function keydown (evt) {
if (!evt) evt = event;
if (evt.ctrlKey && evt.altKey && evt.keyCode === 115) {
alert("CTRL+ALT+F4");
} else if (evt.shiftKey && evt.keyCode === 9) {
alert("Shift+TAB");
}
}
You should use the keydown event to keep track of the keys pressed, and you should use the keyup event to keep track of when the keys are released.
See this example: http://jsfiddle.net/vor0nwe/mkHsU/
(Update: I’m reproducing the code here, in case jsfiddle.net bails:)
The HTML:
<ul id="log">
<li>List of keys:</li>
</ul>
...and the Javascript (using jQuery):
var log = $('#log')[0],
pressedKeys = [];
$(document.body).keydown(function (evt) {
var li = pressedKeys[evt.keyCode];
if (!li) {
li = log.appendChild(document.createElement('li'));
pressedKeys[evt.keyCode] = li;
}
$(li).text('Down: ' + evt.keyCode);
$(li).removeClass('key-up');
});
$(document.body).keyup(function (evt) {
var li = pressedKeys[evt.keyCode];
if (!li) {
li = log.appendChild(document.createElement('li'));
}
$(li).text('Up: ' + evt.keyCode);
$(li).addClass('key-up');
});
In that example, I’m using an array to keep track of which keys are being pressed. In a real application, you might want to delete each element once their associated key has been released.
Note that while I've used jQuery to make things easy for myself in this example, the concept works just as well when working in 'raw' Javascript.
for who needs complete example code. Right+Left added
var keyPressed = {};
document.addEventListener('keydown', function(e) {
keyPressed[e.key + e.location] = true;
if(keyPressed.Shift1 == true && keyPressed.Control1 == true){
// Left shift+CONTROL pressed!
keyPressed = {}; // reset key map
}
if(keyPressed.Shift2 == true && keyPressed.Control2 == true){
// Right shift+CONTROL pressed!
keyPressed = {};
}
}, false);
document.addEventListener('keyup', function(e) {
keyPressed[e.key + e.location] = false;
keyPressed = {};
}, false);
This is not a universal method, but it's usefull in some cases. It's usefull for combinations like CTRL + something or Shift + something or CTRL + Shift + something, etc.
Example: When you want to print a page using CTRL + P, first key pressed is always CTRL followed by P. Same with CTRL + S, CTRL + U and other combinations.
document.addEventListener('keydown',function(e){
//SHIFT + something
if(e.shiftKey){
switch(e.code){
case 'KeyS':
console.log('Shift + S');
break;
}
}
//CTRL + SHIFT + something
if(e.ctrlKey && e.shiftKey){
switch(e.code){
case 'KeyS':
console.log('CTRL + Shift + S');
break;
}
}
});
I used this way (had to check wherever is Shift + Ctrl pressed):
// create some object to save all pressed keys
var keys = {
shift: false,
ctrl: false
};
$(document.body).keydown(function(event) {
// save status of the button 'pressed' == 'true'
if (event.keyCode == 16) {
keys["shift"] = true;
} else if (event.keyCode == 17) {
keys["ctrl"] = true;
}
if (keys["shift"] && keys["ctrl"]) {
$("#convert").trigger("click"); // or do anything else
}
});
$(document.body).keyup(function(event) {
// reset status of the button 'released' == 'false'
if (event.keyCode == 16) {
keys["shift"] = false;
} else if (event.keyCode == 17) {
keys["ctrl"] = false;
}
});
I like to use this snippet, its very useful for writing game input scripts
var keyMap = [];
window.addEventListener('keydown', (e)=>{
if(!keyMap.includes(e.keyCode)){
keyMap.push(e.keyCode);
}
})
window.addEventListener('keyup', (e)=>{
if(keyMap.includes(e.keyCode)){
keyMap.splice(keyMap.indexOf(e.keyCode), 1);
}
})
function key(x){
return (keyMap.includes(x));
}
function checkGameKeys(){
if(key(32)){
// Space Key
}
if(key(37)){
// Left Arrow Key
}
if(key(39)){
// Right Arrow Key
}
if(key(38)){
// Up Arrow Key
}
if(key(40)){
// Down Arrow Key
}
if(key(65)){
// A Key
}
if(key(68)){
// D Key
}
if(key(87)){
// W Key
}
if(key(83)){
// S Key
}
}
Here's an implementation of Bradens answer.
var keys = {}
function handleKeyPress(evt) {
let { keyCode, type } = evt || Event; // to deal with IE
let isKeyDown = (type == 'keydown');
keys[keyCode] = isKeyDown;
// test: enter key is pressed down & shift isn't currently being pressed down
if(isKeyDown && keys[13] && !keys[16]){
console.log('user pressed enter without shift')
}
};
window.addEventListener("keyup", handleKeyPress);
window.addEventListener("keydown", handleKeyPress);
Make the keydown even call multiple functions, with each function checking for a specific key and responding appropriately.
document.keydown = function (key) {
checkKey("x");
checkKey("y");
};
$(document).ready(function () {
// using ascii 17 for ctrl, 18 for alt and 83 for "S"
// ctr+alt+S
var map = { 17: false, 18: false, 83: false };
$(document).keyup(function (e) {
if (e.keyCode in map) {
map[e.keyCode] = true;
if (map[17] && map[18] && map[83]) {
// Write your own code here, what you want to do
map[17] = false;
map[18] = false;
map[83] = false;
}
}
else {
// if u press any other key apart from that "map" will reset.
map[17] = false;
map[18] = false;
map[83] = false;
}
});
});
I'd try adding a keypress Event handler upon keydown. E.g:
window.onkeydown = function() {
// evaluate key and call respective handler
window.onkeypress = function() {
// evaluate key and call respective handler
}
}
window.onkeyup = function() {
window.onkeypress = void(0) ;
}
This is just meant to illustrate a pattern; I won't go into detail here (especially not into browser specific level2+ Event registration).
Post back please whether this helps or not.
If one of keys pressed is Alt / Crtl / Shift you can use this method:
document.body.addEventListener('keydown', keysDown(actions) );
function actions() {
// do stuff here
}
// simultaneous pressing Alt + R
function keysDown (cb) {
return function (zEvent) {
if (zEvent.altKey && zEvent.code === "KeyR" ) {
return cb()
}
}
}
case 65: //A
jp = 1;
setTimeout("jp = 0;", 100);
if(pj > 0) {
ABFunction();
pj = 0;
}
break;
case 66: //B
pj = 1;
setTimeout("pj = 0;", 100);
if(jp > 0) {
ABFunction();
jp = 0;
}
break;
Not the best way, I know.
if you want to find any keypress event with control key you can do like this
onkeypress = (e) =>{
console.log(e);
if(e.ctrlKey && e.code == "KeyZ"){
document.write("do somthing")
} }
Just making something more stable :
var keys = [];
$(document).keydown(function (e) {
if(e.which == 32 || e.which == 70){
keys.push(e.which);
if(keys.length == 2 && keys.indexOf(32) != -1 && keys.indexOf(70) != -1){
alert("it WORKS !!"); //MAKE SOMETHING HERE---------------->
keys.length = 0;
}else if((keys.indexOf(32) == -1 && keys.indexOf(70) != -1) || (keys.indexOf(32) != -1 && keys.indexOf(70) == -1) && (keys.indexOf(32) > 1 || keys.indexOf(70) > 1)){
}else{
keys.length = 0;
}
}else{
keys.length = 0;
}
});
For whoever is using React, here is my solution:
import { useEffect, useState } from "react";
import Backdrop from '#mui/material/Backdrop';
export const Example = () => {
const [backdropOpen, setBackdropOpen] = useState(false);
useEffect(() => {
// Keys that need to be pressed at the same time in order for
// the 'backdropOpen' variable to be 'true'
const keysArr = ['ControlLeft', 'ShiftLeft', 'AltLeft'];
const keysMap = {};
let backdropOpenLocal = false;
const keydownEvent = 'keydown';
const keyupEvent = 'keyup';
const checkKeys = () => {
const keysArePressed = keysArr.every((value) => keysMap[value] === keydownEvent);
if (keysArePressed !== backdropOpenLocal) {
backdropOpenLocal = keysArePressed;
setBackdropOpen(keysArePressed);
}
}
const handleKeyDown = (event) => {
const keyCode = event.code;
if (keysArr.includes(keyCode) && keysMap[keyCode] !== keydownEvent) {
keysMap[keyCode] = keydownEvent;
}
checkKeys();
}
const handleKeyUp = (event) => {
const keyCode = event.code;
if (keysArr.includes(keyCode) && keysMap[keyCode] !== keyupEvent) {
keysMap[keyCode] = keyupEvent;
}
checkKeys();
}
document.addEventListener('keydown', handleKeyDown);
document.addEventListener('keyup', handleKeyUp);
return () => {
document.removeEventListener('keydown', handleKeyDown);
document.removeEventListener('keyup', handleKeyUp);
}
}, []);
return (
<React.Fragmemnt>
<div>
<Backdrop
open={backdropOpen}
>
<span>
It worked!
</span>
</Backdrop>
</div>
</React.Fragmemnt>
);
}
Keep in mind that we need to use the backdropOpenLocal instead of backdropOpen inside the useEffect function, because we want to update the local scoped variable only and keep the state of the scope.
If we update the state of the Example component and try to access backdropOpen, we will have the same value as before, unless we pass in the backdropOpen in the dependency array of useEffect; this would cause the scoped variables inside useEffect to be reset, and we don't want that.
If someone needs easy solution.
let keys = [];
document.addEventListener("keydown", (e) => {
keys.push(e.key);
if (keys.includes("Control") && keys.includes("o")) {
console.log("open");
}
if (keys.includes("Control") && keys.includes("s")) {
console.log("save");
}
});
// clear the keys array
document.addEventListener("keyup", () => {
keys = [];
});
i use cases, ifs and bools. I had a project and this worked great for me
window.addEventListener("keydown", onKeyDown, false);
window.addEventListener("keyup", onKeyUp, false);
function onKeyDown(event) {
var keyCode = event.keyCode;
switch (keyCode) {
case 68: //D
keyd = true;
break;
case 32: //spaaaaaaaaaaaaaaace
keyspace = true;
break;
case 65: //A
keya = true;
break;
case 37:
keya = true;
break;
case 38:
keyspace = true;
break;
case 39:
keyd = true;
break;
}
}
function onKeyUp(event) {
var keyCode = event.keyCode;
switch (keyCode) {
case 68: //dddddd
keyd = false;
break;
case 32: //spaaaaaaaaaaaaaaaaaaaaaace
keyspace = false;
break;
case 65: //aaaaa
keya = false;
break;
case 37:
keya = false;
break;
case 38:
keyspace = false;
break;
case 39:
keyd = false;
break;
}
}
Easiest, and most Effective Method
//check key press
function loop(){
//>>key<< can be any string representing a letter eg: "a", "b", "ctrl",
if(map[*key*]==true){
//do something
}
//multiple keys
if(map["x"]==true&&map["ctrl"]==true){
console.log("x, and ctrl are being held down together")
}
}
//>>>variable which will hold all key information<<
var map={}
//Key Event Listeners
window.addEventListener("keydown", btnd, true);
window.addEventListener("keyup", btnu, true);
//Handle button down
function btnd(e) {
map[e.key] = true;
}
//Handle Button up
function btnu(e) {
map[e.key] = false;
}
//>>>If you want to see the state of every Key on the Keybaord<<<
setInterval(() => {
for (var x in map) {
log += "|" + x + "=" + map[x];
}
console.log(log);
log = "";
}, 300);
Thanks to the help of you fine Overflowians, I fixed up my silly little RNG Addition game and got it working. Now, at one user's suggestion, I'm trying to change the scope of the addition game's code from global to local before I code up the next game; I want each game to be completely contained within its own scope, as I understand that learning to not thoughtlessly contaminate the global scope is a good idea. However, I'm a bit stuck on how to achieve that.
Here's the code for the currently functional addition game:
function beginAdditionChallenge() {
var x = Math.ceil(Math.random()*100);
alert(x);
for (var i = 0; i < 3; i++) {
var a = Number(prompt("Provide the first addend.", ""));
var b = Number(prompt("Provide the second addend.", ""));
if (a + b === x) {
alert("Well done!");
break;
}
else if (a + b !== x && i < 2) {
alert("Please try again.");
}
else {
alert("Derp.");
}
}
}
function initChallenge() {
var button = document.getElementById("challengeButton");
button.addEventListener("click", beginAdditionChallenge);
}
window.addEventListener("load", initChallenge);
And here's my attempt to wrap it, which only succeeds in breaking the game, such that the button doesn't even respond:
window.addEventListener("load", function() {
function beginAdditionChallenge() {
var x = Math.ceil(Math.random()*100);
alert(x);
for (var i = 0; i < 3; i++) {
var a = Number(prompt("Provide the first addend.", ""));
var b = Number(prompt("Provide the second addend.", ""));
if (a + b === x) {
alert("Well done!");
break;
}
else if (a + b !== x && i < 2) {
alert("Please try again.");
}
else {
alert("Derp.");
}
}
}
function initChallenge() {
var button = document.getElementById("challengeButton");
button.addEventListener("click", beginAdditionChallenge);
}
window.addEventListener("load", initChallenge);
});
Functional code is available on JSFiddle here.
Note that the onLoad option in JSFiddle does the same as your 2nd snippet. You'll want to choose one of the No wrap options when binding to 'load' yourself.
And, the issue stems from attempting to bind to 'load' within a 'load' handler:
window.addEventListener("load", function() {
// ...
window.addEventListener("load", initChallenge);
});
When the event is already firing and handling the outer binding, it's too late to add more handlers to it. They won't be cycled through and the event shouldn't occur again.
You'll either want to call initChallenge within the outer event binding:
window.addEventListener("load", function() {
// ...
initChallenge();
});
Or, you can use an IIFE with the inner binding:
(function () {
// ...
window.addEventListener("load", initChallenge);
})();
I would like to be able to trap the double key press (for the Char T for example) in order to do some special processing.I would like the key presses to happen fast enough to not be interpreted as two separate presses, just like the double click.
Any ideas how i can achieve this?
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);
}
}
I know is too late to answer but here goes how I have implemented that:
let pressed;
let lastPressed;
let isDoublePress;
const handleDoublePresss = key => {
console.log(key.key, 'pressed two times');
}
const timeOut = () => setTimeout(() => isDoublePress = false, 500);
const keyPress = key => {
pressed = key.keyCode;
if (isDoublePress && pressed === lastPressed) {
isDoublePress = false;
handleDoublePresss(key);
} else {
isDoublePress = true;
timeOut();
}
lastPressed = pressed;
}
window.onkeyup = key => keyPress(key);