I'm new to JavaScript and I made a simple stopwatch constructor:
function Stopwatch() {
var started = false;
var elapsed;
var start;
d = new Date();
this.duration = function() {
if (started) {
throw "Stopwatch is still running"
} else {
return (elapsed);
}
}
this.start = function() {
if (started) {
throw "Stopwatch has already started";
} else {
start = d.getTime();
started = true;
}
}
this.stop = function() {
if (!started) {
throw "Stopwatch hasn't started";
} else {
elapsed = d.getTime() - start;
started = false;
}
}
this.reset = function() {
started = false;
elapsed = 0;
}
}
let sw = new Stopwatch();
sw.start();
setTimeout(function () {
sw.stop();
console.log(sw.duration());
}, 500);
The logic of the errors works fine, but whenever I call sw.duration(), it always returns zero, and I'm not sure why that is since I'm using var instead of let. Please let me know.
You're calling new Date only once, at the start of the constructor. Use Date.now instead (to get a number, to avoid having to call .getTime), and call it not only when you need to assign to start, but also in .stop, to get elapsed.
function Stopwatch() {
var started = false;
var elapsed;
var start;
this.duration = function() {
if (started) {
throw "Stopwatch is still running"
} else {
return (elapsed);
}
}
this.start = function() {
if (started) {
throw "Stopwatch has already started";
} else {
start = Date.now();
started = true;
}
}
this.stop = function() {
if (!started) {
throw "Stopwatch hasn't started";
} else {
elapsed = Date.now() - start;
started = false;
}
}
this.reset = function() {
started = false;
elapsed = 0;
}
}
let sw = new Stopwatch();
sw.start();
setTimeout(() => {
sw.stop();
console.log(sw.duration());
}, 500);
Related
Is there a way to use setTimeout without using setTimeout inbuilt function?
I don't want to use setInterval or clearInterval either or window.use. I have gone through multiple blogs, but all those use window, setInterval or clearInterval.
For example, the below code works, but I dont want to have window.
const setTimeouts = [];
function customSetTimeout(cb, interval) {
const now = window.performance.now();
const index = setTimeouts.length;
setTimeouts[index] = () => {
cb();
};
setTimeouts[index].active = true;
const handleMessage = (evt) => {
if (evt.data === index) {
if (window.performance.now() - now >= interval) {
window.removeEventListener('message', handleMessage);
if (setTimeouts[index].active) {
setTimeouts[index]();
}
} else {
window.postMessage(index, '*');
}
}
};
window.addEventListener('message', handleMessage);
window.postMessage(index, '*');
return index;
}
const setIntervals = [];
function customSetInterval(cb, interval) {
const intervalId = setIntervals.length;
setIntervals[intervalId] = function () {
if (setIntervals[intervalId].active) {
cb();
customSetTimeout(setIntervals[intervalId], interval);
}
};
setIntervals[intervalId].active = true;
customSetTimeout(setIntervals[intervalId], interval);
return intervalId;
}
function customClearInterval(intervalId) {
if (setIntervals[intervalId]) {
setIntervals[intervalId].active = false;
}
}
console.log("1");
customSetTimeout(function() {
console.log('3s');
}, 3000);
console.log("2");
=======================================
Alternate solution:
But here, again i dont want to use clearInterval and setInterval
var setMyTimeOut = function(foo,timeOut){
console.log('inside time out');
var timer;
var currentTime = new Date().getTime();
var blah=()=>{
if (new Date().getTime() >= currentTime + timeOut) {
console.log('clear interval if');
clearInterval(timer);
foo()
}
console.log('clear interval else');
}
timer= setInterval(blah, 100);
}
console.log("1");
setMyTimeOut(function() {
console.log('3s');
}, 3000);
console.log("2");
Is there way to achieve the same but without the use setInterval and clearInterval?
I use here the requestAnimationFrame with performance.now().
Its not super exact (well setTimeout neither), but it do the work.
function sleep(delay, cb) {
function check(time, delay) {
if(time >= delay) {
cb("done");
return;
}
time = performance.now();
requestAnimationFrame(check.bind(null, time,delay))
}
check(performance.now(), delay + performance.now());
}
sleep(4000, ()=> {
console.log("sleep done");
})
console.log("i do not block the main thread");
You can use a while loop which checks a set time against the current time:
const startTime = new Date().getTime() + 3000;
let currentTime = new Date().getTime();
function customTimeout() {
while (startTime > currentTime) {
currentTime = new Date().getTime();
}
return console.log('3 Seconds')
};
customTimeout();
I am getting an output of 00:20:00 which is correct but my problem now is its not decrementing even when I have subtracted it am i missing something?
$duration=0;
$startime=date('Y-m-d H:i:s');
$end_time=$end_time=date('Y-m-d H:i:s',
strtotime('+'.$duration.'minutes',strtotime($startime)));
$timefirst=strtotime($startime);
$timesecond=strtotime($end_time);
$differenceinseconds=$timesecond-$timefirst;
echo gmdate("H:i:s", $differenceinseconds);
my script
<div id='response'></div>
<script type="text/javascript">
setInterval(function(){
var xmlhttp=new XMLHttpRequest();
xmlhttp.open("GET",'responseTime.php',false);
xmlhttp.send(null);
document.getElementById('response').innerHTML=xmlhttp.responseText;
},1000);
</script>
As RiggsFolly mentioned why waste servers time running a timer.
Here is what you can do in javascript,
<div id="stopwatch"></div>
<script>
var Stopwatch = function (elem, target, options) {
var timer = createTimer(),
offset,
clock,
interval;
// default options
options = options || {};
options.delay = options.delay || 1;
// append elements
elem.appendChild(timer);
// initialize
reset();
// private functions
function createTimer() {
var interval = 20 ; // 20 seconds
var element = document.createElement("progress");
element.setAttribute("max",interval);
return element;
}
function start() {
if (!interval) {
offset = Date.now();
interval = setInterval(update, options.delay);
}
}
function stop() {
if (interval) {
clearInterval(interval);
interval = null;
}
}
function reset() {
clock = 0;
render();
}
function update() {
clock += delta();
render();
}
function render() {
timer.value = parseInt(clock / 1000);
if(timer.value==interval){
// This is the point where timer ends, put your further code in here.
}
}
function delta() {
var now = Date.now(),
d = now - offset;
offset = now;
return d;
}
// public API
this.start = start;
this.stop = stop;
this.reset = reset;
};
var elem = document.getElementById("stopwatch");
var timer = new Stopwatch(elem, {delay: 10});
timer.start();
</script>
I've built a series of timers that are designed to be started, paused and resumed on cue. Numbers update dynamically on my page when the timer ticks up. The issue I'm having is figuring out how to get the timer to start from where it left off before I paused it. I can get it to restart from scratch, but I unsure how to take the paused Date.now() value, and work it into the formula to display the correct value. It will be something stupid that I just cant figure out.
function ticking2(num) {
//IF TIMER IS PAUSED CANCEL THE ANIMATION FRAME
if (timerObjArray[num].paused == true) {
timerObjArray[num].restartTime = Date.now();
cancelAnimationFrame(id);
} else if (timerObjArray[num].paused == false) {
timerObjArray[num].initialTime = Date.now()
if (timerObjArray[num].restartTime != 0) {
//THIS IS THE LINE WHERE I AM HAVING TROUBLE
timerObjArray[num].milli = ((timerObjArray[num].initialTime - timerObjArray[num].initialDate) - (timerObjArray[num].initialTime - timerObjArray[num].restartTime)) / 1000;
} else {
timerObjArray[num].milli = ((timerObjArray[num].initialTime - timerObjArray[num].initialDate ) / 1000);
}
//THIS FUNCTION TAKES THE MS VALUE AND CONVERTS IT TO HH:MM:SS
convert(num, timerObjArray[num].milli * 1000);
id = requestAnimationFrame(function() {
ticking2(num);
});
}
}
Thanks for the help.
I don't have enough information so, I made a simple implementation. You can look at this to help determine what you're missing. You're welcome to use it.
Timer fiddle
Utility:
var timer = (function() {
let _timers = {};
let pub = {
start : function(id) {
if(!_timers[id]) _timers[id] = {on:true, intervals:[{start:new Date()}] };
else if(_timers[id].on) throw 'timer is already started: ' + id;
else {
_timers[id].on = true;
_timers[id].intervals.push({start:new Date()});
}
},
stop : function(id) {
if(!_timers[id]) throw 'timer does not exist, cannot be stopped: ' + id;
else if(!_timers[id].on) throw 'timer is already stopped: ' + id;
else {
_timers[id].on = false;
let interval = _timers[id].intervals[_timers[id].intervals.length -1];
interval.stop = new Date();
interval.total = interval.stop - interval.start;
}
},
read : function(id) {
if(!_timers[id]) throw 'timer does not exist, cannot be read: ' + id;
let total = 0;
for(let i=0; i<_timers[id].intervals.length; i++) {
if(_timers[id].intervals[i].total) total += _timers[id].intervals[i].total;
else total += (new Date()) - _timers[id].intervals[i].start;
}
return { intervals:_timers[id].intervals, total: total };
},
delete: function(id) {
if(!_timers[id]) throw 'timer does not exist, cannot be deleted: ' + id;
delete _timers[id];
}
};
return pub;
})();
Example usage:
$('.start').on('click', function(){
timer.start(123);
});
$('.stop').on('click', function(){
timer.stop(123);
});
$('.clear').on('click', function(){
timer.delete(123);
$('input').val('');
});
setInterval(function(){
let result = null;
try//obviously not a great pattern
{
result = timer.read(123);
} catch(ex){}
if(result) {
$('input').val(result.total);
}
}, 35);
I'm having trouble with designing a class which exposes its actions through callbacks. Yes my approach works for me but also seems too complex.
To illustrate the problem I've drawn the following picture. I hope it is useful for you to understand the class/model.
In my approach, I use some arrays holding user defined callback functions.
....
rocket.prototype.on = function(eventName, userFunction) {
this.callbacks[eventName].push(userFunction);
}
rocket.prototype.beforeLunch = function(){
userFunctions = this.callbacks['beforeLunch']
for(var i in userFunctions)
userFunctions[i](); // calling the user function
}
rocket.prototype.lunch = function() {
this.beforeLunch();
...
}
....
var myRocket = new Rocket();
myRocket.on('beforeLunch', function() {
// do some work
console.log('the newspaper guys are taking pictures of the rocket');
});
myRocket.on('beforeLunch', function() {
// do some work
console.log('some engineers are making last checks ');
});
I'm wondering what the most used approach is. I guess I could use promises or other libraries to make this implementation more understandable. In this slide using callbacks is considered evil. http://www.slideshare.net/TrevorBurnham/sane-async-patterns
So, should I use a library such as promise or continue and enhance my approach?
var Rocket = function () {
this.timer = null;
this.velocity = 200;
this.heightMoon = 5000;
this.goingToMoon = true;
this.rocketStatus = {
velocity: null,
height: 0,
status: null
};
this.listener = {
};
}
Rocket.prototype.report = function () {
for (var i in this.rocketStatus) {
console.log(this.rocketStatus[i]);
};
};
Rocket.prototype.on = function (name,cb) {
if (this.listener[name]){
this.listener[name].push(cb);
}else{
this.listener[name] = new Array(cb);
}
};
Rocket.prototype.initListener = function (name) {
if (this.listener[name]) {
for (var i = 0; i < this.listener[name].length; i++) {
this.listener[name][i]();
}
return true;
}else{
return false;
};
}
Rocket.prototype.launch = function () {
this.initListener("beforeLaunch");
this.rocketStatus.status = "Launching";
this.move();
this.initListener("afterLaunch");
}
Rocket.prototype.move = function () {
var that = this;
that.initListener("beforeMove");
if (that.goingToMoon) {
that.rocketStatus.height += that.velocity;
}else{
that.rocketStatus.height -= that.velocity;
};
that.rocketStatus.velocity = that.velocity;
if (that.velocity != 0) {
that.rocketStatus.status = "moving";
}else{
that.rocketStatus.status = "not moving";
};
if (that.velocity >= 600){
that.crash();
return;
}
if (that.rocketStatus.height == 2000 && that.goingToMoon)
that.leaveModules();
if (that.rocketStatus.height == that.heightMoon)
that.landToMoon();
if (that.rocketStatus.height == 0 && !that.goingToMoon){
that.landToEarth();
return;
}
that.report();
that.initListener("afterMove");
that.timer = setTimeout(function () {
that.move();
},1000)
}
Rocket.prototype.stop = function () {
clearTimeout(this.timer);
this.initListener("beforeStop");
this.velocity = 0;
this.rocketStatus.status = "Stopped";
console.log(this.rocketStatus.status)
this.initListener("afterStop");
return true;
}
Rocket.prototype.crash = function () {
this.initListener("beforeCrash");
this.rocketStatus.status = "Crashed!";
this.report();
this.stop();
this.initListener("afterCrash");
}
Rocket.prototype.leaveModules = function () {
this.initListener("beforeModules");
this.rocketStatus.status = "Leaving Modules";
this.initListener("afterModules");
}
Rocket.prototype.landToMoon = function () {
this.initListener("beforeLandToMoon");
this.rocketStatus.status = "Landing to Moon";
this.goingToMoon = false;
this.initListener("afterLandToMoon");
}
Rocket.prototype.landToEarth = function () {
this.initListener("beforeLandToEarth");
this.stop();
this.rocketStatus.status = "Landing to Earth";
this.initListener("afterLandToEarth");
}
Rocket.prototype.relaunch = function () {
this.initListener("beforeRelaunch");
this.timer = null;
this.velocity = 200;
this.heightMoon = 5000;
this.goingToMoon = true;
this.rocketStatus = {
velocity: 200,
height: 0,
status: "relaunch"
};
this.launch();
this.initListener("afterRelaunch");
}
init;
var rocket = new Rocket();
rocket.on("afterLaunch", function () {console.log("launch1")})
rocket.on("afterLandToMoon", function () {console.log("land1")})
rocket.on("beforeLandToEarth", function () {console.log("land2")})
rocket.on("afterMove", function () {console.log("move1")})
rocket.on("beforeLaunch", function () {console.log("launch2")})
rocket.launch();
You can add any function before or after any event.
This is my solution for this kinda problem. I am not using any special methods anything. I was just wonder is there any good practise for this like problems. I dig some promise,deferred but i just can't able to to this. Any ideas ?
I'm trying to figure out a way to emulate AS3's Timer class.
If you're not familiar, one of the cool things you can do is add duration to the timer even if it's already running. This functionality has a lot of very nice uses.
Anyone have any thoughts on doing this in js?
I'm not familiar with this class, but you can easily create something similar in JavaScript:
function Timer(callback, time) {
this.setTimeout(callback, time);
}
Timer.prototype.setTimeout = function(callback, time) {
var self = this;
if(this.timer) {
clearTimeout(this.timer);
}
this.finished = false;
this.callback = callback;
this.time = time;
this.timer = setTimeout(function() {
self.finished = true;
callback();
}, time);
this.start = Date.now();
}
Timer.prototype.add = function(time) {
if(!this.finished) {
// add time to time left
time = this.time - (Date.now() - this.start) + time;
this.setTimeout(this.callback, time);
}
}
Usage:
var timer = new Timer(function() { // init timer with 5 seconds
alert('foo');
}, 5000);
timer.add(2000); // add two seconds
Clear the timeout, then set a new timeout to the new desired end time.
Wrap the function with another one, and when the timer runs out, test to see if an extra time variable has been set. If it has, start again with the new time, otherwise execute the function.
A quickly hacked together script might look like:
function test() {
tim = new timer(function () { alert('hello'); }, 5000);
}
function extend() {
if (tim) { tim.addTime(5000); }
}
function timer(func, time) {
var self = this,
execute = function () {
self.execute()
};
this.func = func;
this.extraTime = 0;
setTimeout(execute, time);
};
timer.prototype.execute = function () {
var self = this,
execute = function () {
self.execute()
};
if (this.extraTime) {
setTimeout(execute, this.extraTime);
this.extraTime = 0;
} else {
this.func();
}
};
timer.prototype.addTime = function (time) {
this.extraTime += time;
}
<input type="button" value="Start" onclick="test()">
<input type="button" value="Extend" onclick="extend()">
There you go hope it helps :) just call setInterval with the time you want to have.
Edit: added stop and start in case you want to stop your loop :p
function Timer(defaultInterval, callback){
var interval = defaultInterval;
var running = true;
function loop(){
callback();
if(running){
setTimeout(function(){
loop();
}, interval);
}
}
loop();
return {
setInterval: function(newInterval){
interval = newInterval;
},
stop: function(){
running = false;
},
start: function(){
if(running===false){
running = true;
loop();
}
},
add: function(milliToAdd){
interval += milliToAdd*1;
}
}
}
var myTimer = Timer(250, function() { process code here });
myTimer.setInterval(1000); // sets interval to 1 second
myTimer.stop(); // stops the function
myTimer.start(); // re-starts the loop;
function Timer(func, delay) {
var done = false;
var callback = function() {
done = true;
return func();
};
var startTime = Date.now();
var timeout = setTimeout(callback, delay);
this.add = function(ms) {
if (!done) {
this.cancel();
delay = delay - (Date.now() - startTime) + ms;
timeout = setTimeout(callback, delay);
}
};
this.cancel = function() {
clearTimeout(timeout);
};
this.immediately = function() {
if (!done) {
this.cancel();
callback();
}
};
};
quick test in the console
start = Date.now();
t = new Timer(function() { console.log(Date.now() - start); }, 1000);
t.add(200);
start = Date.now();
t = new Timer(function() { console.log(Date.now() - start); }, 1000000);
t.immediately();
t.immediately();
you can add negative times too.
start = Date.now();
t = new Timer(function() { console.log(Date.now() - start); }, 1000);
t.add(-200);
Here's my shot. It keeps track of when the timer was set, and adds the difference to the specified time when you add time.
var Timer = {
set: function(p_function, p_time)
{
var d = new Date();
this.timeStarted = d.getTime();
this.func = p_function;
this.timeout = setTimeout(p_function, p_time);
console.log('timer started at ' + (this.timeStarted / 1000) + ' seconds');
},
add: function(p_time)
{
var d = new Date(),
diff = d.getTime() - this.timeStarted,
newTime = diff + p_time;
if (this.timeout)
{
clearTimeout(this.timeout);
}
this.timeout = setTimeout(this.func, newTime);
this.timeStarted = d.getTime();
}
};
var myTimer = Object.create(Timer);
myTimer.set(function() {
var d = new Date();
console.log('Timer fired at ' + (d.getTime() / 1000) + ' seconds');
}, 10000);
setTimeout(function () {
myTimer.add(5000);
}, 5000);
Here's a jsFiddle
Please note that due to overhead of calculation and function calls, this may be a couple milliseconds off.
I decided to throw my little rubber ducky into the pool.
var setTimeout2 = function(callback, delay) {
this.complete = false;
this.callback = callback;
this.delay = delay;
this.timeout = false;
this.dotimeout = function() {
this.timeout = setTimeout(function() {
this.complete = true;
this.callback.call();
}, this.delay);
};
this.start = Date.now();
this.add = function(delay) {
if (!this.complete) {
this.delay = this.delay - (Date.now() - this.start) + delay;
clearTimeout(this.timeout);
this.dotimeout.call();
}
};
return this;
};
usage
var start = Date.now();
var to = setTimeout2(function() {
document.write(Date.now() - start);
}, 3000);
to.add(3000);
similar to this approach but a little more compact / no proto