If you want an equal interval, your loop is fine, you just need to fix the math for calculating the timeout:
const btn = document.getElementById('btn');
btn.addEventListener('click', function(){
for (let index = 10; index > 0; index--) {
setTimeout(() => {
console.log(index)
}, 1000*(10-index));
}
})<div class="app">
<button id="btn">click</button>
</div>That will count down from 10 to 1 once every second, just change the 1000 as needed if you want it to be faster or slower.
Note that the order of the loop doesn't actually matter here (aside from a few ms difference in execution time) since it's asynchronous - you could use a non-reversed loop and still get the same result to the human eye.
Answer from John Montgomery on Stack OverflowIf you want an equal interval, your loop is fine, you just need to fix the math for calculating the timeout:
const btn = document.getElementById('btn');
btn.addEventListener('click', function(){
for (let index = 10; index > 0; index--) {
setTimeout(() => {
console.log(index)
}, 1000*(10-index));
}
})<div class="app">
<button id="btn">click</button>
</div>That will count down from 10 to 1 once every second, just change the 1000 as needed if you want it to be faster or slower.
Note that the order of the loop doesn't actually matter here (aside from a few ms difference in execution time) since it's asynchronous - you could use a non-reversed loop and still get the same result to the human eye.
If you use promises and async/await you can avoid the setTimeout overload and have precise control. The difference between this and John Montgomery's answer is this doesn't care how many times you loop. Do 10000 if you want, you won't get 10000 setTimeouts running at the same time.
const btn = document.getElementById('btn');
const wait = time=>new Promise(resolve=>setTimeout(resolve,time))
btn.addEventListener('click', async function(){
for (let index = 10; index > 0; index--) {
await wait(1000)
console.log(index)
}
})<div class="app">
<button id="btn">click</button>
</div>Async functions allow you to use the await keyword. This is a neat new feature in javascript that let's you write async code (like setTimout) as if it was sync.
const wait = time=>new Promise(resolve=>setTimeout(resolve,time))
is a fairly common helper function developers keep around for times you need to just wait some amount of time and then do something. By await'ing the wait(1000) function, I hang the execution of the loop until the time is done.
Videos
It's not that i-- is faster than i++. Actually, they're both equally fast.
What takes time in ascending loops is evaluating, for each i, the size of your array. In this loop:
for(var i = array.length; i--;)
You evaluate .length only once, when you declare i, whereas for this loop
for(var i = 1; i <= array.length; i++)
you evaluate .length each time you increment i, when you check if i <= array.length.
In most cases you shouldn't even worry about this kind of optimization.
This guy compared a lot of loops in javascript, in a lot of browsers. He also has a test suite so you can run them yourself.
In all cases (unless I missed one in my read) the fastest loop was:
var i = arr.length; //or 10
while(i--)
{
//...
}
You can use it like this
for (var i = 10; i >= 0; i--)
But I'm not sure why are you doing so because you are not using this variable inside your loop so I think it doesn't make any difference to the output as you loop going to run 10 times either way.
If I could guess then I think you want to print the stars in reverse order of quantity. That means you want to have maximum stars in first row then -1 in second and so on.. If so then you need to reverse the order of inner loop only like this
function seethestars1() {
var stars = document.getElementById("emptytext2");
for (var i = 0; i <= 10; i++) {
for (var j = 10; j > i; j--) {
stars.value += "*";
}
stars.value += "\n";
}
}
Js Fiddle Demo
Just try the following code for seethestarts1 method.
function seethestars1() {
for (var i = 0; i <= 10; i++) {
for (var j = i; j > 0; j--) {
document.getElementById("emptytext2").value += "*";
}
document.getElementById("emptytext2").value += "\n";
}
}