Dot dotdot dotdotdot as loading?

I wanna create some loading dots, like this:

At 0000 miliseconds the span content is: .

At 0100 miliseconds the span content is: ..

At 0200 miliseconds the span content is: ...

In a loop.

What is the best / easiest way to make it?

<span id="wait">.</span>

<script>
var dots = window.setInterval( function() {
    var wait = document.getElementById("wait");
    if ( wait.innerHTML.length > 3 ) 
        wait.innerHTML = "";
    else 
        wait.innerHTML += ".";
    }, 100);
</script>

---

Or you can get fancy and have them go forward and back:

<span id="wait">.</span>

<script>
    window.dotsGoingUp = true;
    var dots = window.setInterval( function() {
        var wait = document.getElementById("wait");
        if ( window.dotsGoingUp ) 
            wait.innerHTML += ".";
        else {
            wait.innerHTML = wait.innerHTML.substring(1, wait.innerHTML.length);
            if ( wait.innerHTML === "")
                window.dotsGoingUp = true;
        }
        if ( wait.innerHTML.length > 9 )
            window.dotsGoingUp = false;
        
        
        
        }, 100);
    </script>

Or you could make them go back and forth randomly:

<span id="wait">.</span>

<script type="text/javascript">
    var dots = window.setInterval( function() {
        var wait = document.getElementById("wait");
        if ( Math.random() < .7 )
            wait.innerHTML += ".";
        else
            wait.innerHTML = wait.innerHTML.substring(1, wait.innerHTML.length);
        }, 100);
</script>

Or I could get a life and stop posting additional snippets.... :D

As Ivo said in the comments, you need to clear the interval at some point, especially if you are not loading a new page after the waiting is finished. :D

Or.. you can do it with CSS ;)

<p class="loading">Loading</p>

.loading:after {
  content: ' .';
  animation: dots 1s steps(5, end) infinite;
}

@keyframes dots {
  0%, 20% {
    color: rgba(0,0,0,0);
    text-shadow:
      .25em 0 0 rgba(0,0,0,0),
      .5em 0 0 rgba(0,0,0,0);}
  40% {
    color: white;
    text-shadow:
      .25em 0 0 rgba(0,0,0,0),
      .5em 0 0 rgba(0,0,0,0);}
  60% {
    text-shadow:
      .25em 0 0 white,
      .5em 0 0 rgba(0,0,0,0);}
  80%, 100% {
    text-shadow:
      .25em 0 0 white,
      .5em 0 0 white;}}

Codepen sample

Example: https://codepen.io/lukaszkups/pen/NQjeVN

You can animate css content too!

p span:before {
    animation: dots 2s linear infinite;
    content: '';
  }

  @keyframes dots {
    0%, 20% {
      content: '.';
    }
    40% {
      content: '..';
    }
    60% {
      content: '...';
    }
    90%, 100% {
      content: '';
    }
}

<p>Loading<span></span></p>

Example: http://jsfiddle.net/subTZ/

var span = document.getElementById('myspan');

var int = setInterval(function() {
    if ((span.innerHTML += '.').length == 4) 
        span.innerHTML = '';
    //clearInterval( int ); // at some point, clear the setInterval
}, 100);

This is similar to Veiko Jääger's solution. With this solution, the color of the dots is the same as the text it associates with.

This is a test

    let span = document.querySelector('span');
    	i = 0;
    
    setInterval(() => {
    	span.innerText = Array(i = i > 2 ? 0 : i + 1).fill('.').join('');
    }, 500)

loading<span></span>

In my mind, the easiest way is an if/else statement.

However, a bit math to calculate the dots-length and the famous Array.join-hack to repeat the dot-char, should do the trick too.

function dotdotdot(cursor, times, string) {
  return Array(times - Math.abs(cursor % (times * 2) - times) + 1).join(string);
}

var cursor = 0;
setInterval(function () {
  document.body.innerHTML = dotdotdot(cursor++, 3, '.')
}, 100);

You could improve the readability a bit, by wrapping the "count-up-and-down"-part and "string-repetition" in separate functions.

With String.prototype.repeat() you can do:

var element = document.querySelector(...);
var counter = 0;

var intervalId = window.setInterval(function() {
    counter += 1
    element.innerHTML = '.'.repeat(1 + counter % 3)
}, 350);

// Use the following to clear the interval
window.clearInterval(intervalId)

Note: String.prototype.repeat() is currently not supported in < IE11