Dynamically change animation speed

Question

For teaching myself javascript (and for getting/giving more insight in the field of astronomy :) ), I am setting up a page that displays relative positions of sun and moon. Right now, the speed of the sun and moon movement is still fixed, but I would really like to make this dynamically user-definable via an input field. So, the initial speed is '30', and a user can speed this up or slow this down. Obviously, the ratio between sun and moon must stay fixed. I tried a lot of things (see some relics in the code, but I can't get it to work.

Anyone with more experience with javascript can assist me in doing this? Also, I notice CPU usage gets very high during this animation. Are there simple steps in making this script more efficient?

 var dagen = 0; function speed($this){ var speedSetting = $this.value; //alert(speedSetting); //return per; } function periode(bolletje, multiplier=30){ if (bolletje == 'zon'){var per = (multiplier*24/2);} if (bolletje == 'maan'){var per = (multiplier*24*29.5/2);} return per; } function step(delta) { elem.style.height = 100*delta + '%' } function animate(opts) { var start = new Date var id = setInterval(function() { var timePassed = new Date - start var progress = timePassed / opts.duration if (progress > 1) progress = 1 var delta = opts.delta(progress) opts.step(delta) if (progress == 1) { clearInterval(id) } }, opts.delay || 10) } function terugweg(element, delta, duration) { var to = -300; var bolletje = element.getAttribute('id'); per = periode(bolletje); document.getElementById(bolletje).style.background='transparent'; animate({ delay: 0, duration: duration || per, //1 sec by default delta: delta, step: function(delta) { element.style.left = ((to*delta)+300) + "px" } }); if(bolletje == 'zon'){ dagen ++; } bolletje = element; document.getElementById('dagen').innerHTML = dagen; //setInterval(function (element) { setTimeout(function (element) { move(bolletje, function(p) {return p}) }, per); } function move(element, delta, duration) { var to = 300; var bolletje = element.getAttribute('id'); per = periode(bolletje); document.getElementById(bolletje).style.background='yellow'; animate({ delay: 0, duration: duration || per, //1 sec by default delta: delta, step: function(delta) { element.style.left = to*delta + "px" } }); bolletje = element; //setInterval(function (element) { setTimeout(function (element) { terugweg(bolletje, function(p) {return p}) }, per); }

 hr{clear: both;} form{display: block;} form label{width: 300px; float: left; clear: both;} form input{float: right;} .aarde{width: 300px; height: 300px; border-radius: 150px; background: url('https://domain.com/img/aarde.png');} #zon{width: 40px; height: 40px; background: yellow; border: 2px solid yellow; border-radius: 20px; position: relative; margin-left: -20px; top: 120px;} #maan{width: 30px; height: 30px; background: yellow; border: 2px solid yellow; border-radius: 16px; position: relative; margin-left: -15px; top: 115px;}

 <form> <div onclick="move(this.children[0], function(p) {return p}), move(this.children[1], function(p) {return p})" class="aarde"> <div id="zon"></div> <div id="maan"></div> </div> Dagen: <span id="dagen">0</span> </form> <form> <label><input id="snelheid" type="range" min="10" max="300" value="30" oninput="speed(this)">Snelheid: <span id="snelheidDisplay">30</span></label> </form>

Answer 1

First, change onlick to oninput in speed input tag.

<input id="snelheid" type="number"  value="30" oninput="speed(this)">

And in your speed() function set multiplier = $this.value . multiplier should be global:

var multiplier = 30;
function speed($this){
  console.log($this.value);
    multiplier = $this.value;
    //alert(speedSetting);
    //return per;
}
function periode(bolletje){
    if (bolletje == 'zon'){var per = (multiplier*24/2);}
    if (bolletje == 'maan'){var per = (multiplier*24*29.5/2);}
    return per;
}

Here is an example: https://jsfiddle.net/do4n9L03/2/

Note: multiplier is not speed, it is delay. If you increase it it become slower