smooth scrolling - How to smoothly scroll to an element in pure JavaScript

Question

I want to smoothly scroll to an element without using jQuery – just pure javascript. I would like a generic function to be able to both scroll down and scroll up smoothly to a specific position in the document.

I know I can use the following in jQuery:

$('html, body').animate({
     scrollTop: $('#myelementid').offset().top
}, 500);

How would I do it with just javascript?

This is what I am trying to do:

function scrollToHalf(){
  //what do I do?
}
function scrollToSection(){
 //What should I do here?
}

<input type="button" onClick="scrollToHalf()" value="Scroll To 50% of Page">
    <br>
    <input type="button" onClick="scrollToSection()" value="Scroll To Section1">
    <section style="margin-top: 1000px;" id="section1">
      This is a section
</section>

Answer 1

To scroll to a certain position in an exact amount of time, window.requestAnimationFrame can be put to use, calculating the appropriate current position each time. setTimeout can be used to a similar effect when requestAnimationFrame is not supported.

/*
   @param pos: the y-position to scroll to (in pixels)
   @param time: the exact amount of time the scrolling will take (in milliseconds)
*/
function scrollToSmoothly(pos, time) {
    var currentPos = window.pageYOffset;
    var start = null;
    if(time == null) time = 500;
    pos = +pos, time = +time;
    window.requestAnimationFrame(function step(currentTime) {
        start = !start ? currentTime : start;
        var progress = currentTime - start;
        if (currentPos < pos) {
            window.scrollTo(0, ((pos - currentPos) * progress / time) + currentPos);
        } else {
            window.scrollTo(0, currentPos - ((currentPos - pos) * progress / time));
        }
        if (progress < time) {
            window.requestAnimationFrame(step);
        } else {
            window.scrollTo(0, pos);
        }
    });
}

Demo:

/*
   @param time: the exact amount of time the scrolling will take (in milliseconds)
   @param pos: the y-position to scroll to (in pixels)
*/
function scrollToSmoothly(pos, time) {
    var currentPos = window.pageYOffset;
    var start = null;
    if(time == null) time = 500;
    pos = +pos, time = +time;
    window.requestAnimationFrame(function step(currentTime) {
        start = !start ? currentTime : start;
        var progress = currentTime - start;
        if (currentPos < pos) {
            window.scrollTo(0, ((pos - currentPos) * progress / time) + currentPos);
        } else {
            window.scrollTo(0, currentPos - ((currentPos - pos) * progress / time));
        }
        if (progress < time) {
            window.requestAnimationFrame(step);
        } else {
            window.scrollTo(0, pos);
        }
    });
}

<button onClick="scrollToSmoothly(document.querySelector('div').offsetTop, 300)">
Scroll To Div (300ms)
</button>
<button onClick="scrollToSmoothly(document.querySelector('div').offsetTop, 200)">
Scroll To Div (200ms)
</button>
<button onClick="scrollToSmoothly(document.querySelector('div').offsetTop, 100)">
Scroll To Div (100ms)
</button>
<button onClick="scrollToSmoothly(document.querySelector('div').offsetTop, 50)">
Scroll To Div (50ms)
</button>
<button onClick="scrollToSmoothly(document.querySelector('div').offsetTop, 1000)">
Scroll To Div (1000ms)
</button>
<div style="margin: 500px 0px;">
DIV<p/>
<button onClick="scrollToSmoothly(0, 500)">
Back To Top
</button>
<button onClick="scrollToSmoothly(document.body.scrollHeight)">
Scroll To Bottom
</button>
</div>
<div style="margin: 500px 0px;">
</div>
<button style="margin-top: 100px;" onClick="scrollToSmoothly(500, 3000)">
Scroll To y-position 500px (3000ms)
</button>