Smooth Scroll to Top in JavaScript

Smooth Scroll to Top in JavaScript
Code Snippet: Scrolling Up Button
Author: Wiktor
Published: January 11, 2024
Last Updated: January 22, 2024
Downloads: 2,715
License: MIT
Edit Code online: View on CodePen
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This JavaScript code snippet helps you to create a smooth scroll to the top button. It dynamically adds back to the top page button on a webpage. You just need to add JS function to your web project, then this plugin dynamically adds back to the top button.

It comes with following features:

  • 3 animate modes: [“normal”|”linear”|false]
  • Customize your animation with available settings – make it snappy or fluent
  • Double click to skip the animation
  • Every next single click adds initial speed
  • Stop scroll animation by dragging down the scroll bar
  • Stop scroll animation by mouse wheel down
  • Animated button fade-in-out on scroll

How to Create Smooth Scroll to Top in JavaScript

1. First of all, add the following CSS styles to your project:

/* CSS */
@import url(https://fonts.googleapis.com/css?family=Open+Sans);
body{
  font-family: 'Open Sans', sans-serif;
  font-size: 1.2rem;
  line-height: 2rem;
  height: 100%;
  position: relative;
}

.scroll-button{
  box-sizing: border-box;
  font-size: 1.2rem;
  line-height: 2rem;
  padding: 5px;
  width: 80px;
  height: 80px;
  right: 20px;
  bottom: 20px;
  visibility: visible;
  filter: alpha(opacity=50);
  filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=50);
  opacity: 0.5;
  cursor: pointer;
  transition: all 1.2s;
  -webkit-transition: all 1.2s;
  -moz-transition: all 1.2s;
  -ms-transition: all 1.2s;
  -o-transition: all 1.2s;
}

/* STYLE BUTTON 1 - filled in */
/* .scroll-button{
  background: rgb(249, 104, 211);
  border: none;
  color: white;
} */

/* STYLE BUTTON 2 - only outlines */
.scroll-button{
  background: none;
  border: solid 2px rgb(210, 104, 211);
  color: rgb(249, 104, 211);
}

/* SHAPE BUTTON 1 - round */
/* .scroll-button{
  border-radius: 50%;
} */

/* SHAPE BUTTON 2 - square */
.scroll-button{
  border-radius: 0%;
}

/* POSITION BUTTON 1 - on the bottom of the screen */
.scroll-button{
  position: fixed;
}

/* POSITION BUTTON 2 - on the bottom of the page */
/* .scroll-button{
  position: absolute;
} */





.scroll-button:hover{
  filter: alpha(opacity=100);
  filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=100);
  opacity: 1;
}

.scroll-button--hidden{
  filter: alpha(opacity=0);
  filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=0);
  opacity: 0;
  visibility: hidden;
}

3. Then, add the following JavaScript code and done.

// PURE JAVASCRIPT "Scroller" CLASS (OOP)
/*
* Author: Wiktor Liszkiewicz
*/

function Scroller(options) {
  this.options = options;
  this.button = null;
  this.stop = false;
}

Scroller.prototype.constructor = Scroller;

Scroller.prototype.createButton = function() {

  this.button = document.createElement('button');
  this.button.classList.add('scroll-button');
  this.button.classList.add('scroll-button--hidden');
  this.button.textContent = "^";
  document.body.appendChild(this.button);
}
  
Scroller.prototype.init = function() {
  this.createButton();
  this.checkPosition();
  this.click();
  this.stopListener();
}

Scroller.prototype.scroll = function() {
  if (this.options.animate == false || this.options.animate == "false") {
    this.scrollNoAnimate();
    return;
  }
  if (this.options.animate == "normal") {
    this.scrollAnimate();
    return;
  }
  if (this.options.animate == "linear") {
    this.scrollAnimateLinear();
    return;
  }
}
Scroller.prototype.scrollNoAnimate = function() {
  document.body.scrollTop = 0;
  document.documentElement.scrollTop = 0;
}
Scroller.prototype.scrollAnimate = function() {
  if (this.scrollTop() > 0 && this.stop == false) {
    setTimeout(function() {
      this.scrollAnimate();
      window.scrollBy(0, (-Math.abs(this.scrollTop())/this.options.normal['steps']));
    }.bind(this), (this.options.normal['ms']));
  }
}
Scroller.prototype.scrollAnimateLinear = function() {
  if (this.scrollTop() > 0 && this.stop == false) {
    setTimeout(function() {
      this.scrollAnimateLinear();
      window.scrollBy(0, -Math.abs(this.options.linear['px']));
    }.bind(this), this.options.linear['ms']);
  }
}

Scroller.prototype.click = function() {
  
  this.button.addEventListener("click", function(e) {
    e.stopPropagation();
      this.scroll();
  }.bind(this), false);
  
  this.button.addEventListener("dblclick", function(e) {
    e.stopPropagation();
      this.scrollNoAnimate();
  }.bind(this), false);
  
}

Scroller.prototype.hide = function() {
  this.button.classList.add("scroll-button--hidden");
}

Scroller.prototype.show = function() {
  this.button.classList.remove("scroll-button--hidden");
}

Scroller.prototype.checkPosition = function() {
  window.addEventListener("scroll", function(e) {
    if (this.scrollTop() > this.options.showButtonAfter) {
      this.show();
    } else {
      this.hide();
    }
  }.bind(this), false);
}

Scroller.prototype.stopListener = function() {
  
  // stop animation on slider drag
  var position = this.scrollTop();
  window.addEventListener("scroll", function(e) {
    if (this.scrollTop() > position) {
      this.stopTimeout(200);
    } else {
      //...
    }
    position = this.scrollTop();
  }.bind(this, position), false);

  // stop animation on wheel scroll down
  window.addEventListener("wheel", function(e) {
    if(e.deltaY > 0) this.stopTimeout(200);
  }.bind(this), false);
}

Scroller.prototype.stopTimeout = function(ms){
   this.stop = true;
         // console.log(this.stop); //
   setTimeout(function() {
     this.stop = false;
           console.log(this.stop); //
   }.bind(this), ms);
}

Scroller.prototype.scrollTop = function(){
   var curentScrollTop = document.documentElement.scrollTop || document.body.scrollTop;
  return curentScrollTop;
}



// ------------------- USE EXAMPLE ---------------------
// *Set options
var options = {
  'showButtonAfter': 200, // show button after scroling down this amount of px
  'animate': "normal", // [false|normal|linear] - for false no aditional settings are needed
  // easy out effect
  'normal': { // applys only if [animate: normal] - set scroll loop "distanceLeft"/"steps"|"ms"
    'steps': 15, // more "steps" per loop => slower animation
    'ms': 1000/60 // less "ms" => quicker animation, more "ms" => snapy
  },
  // linear effect
  'linear': { // applys only if [animate: linear] - set scroll "px"|"ms"
    'px': 80, // more "px" => quicker your animation gets
    'ms': 1000/60 // Less "ms" => quicker your animation gets, More "ms" =>
  }, 
};
// *Create new Scroller and run it.
var scroll = new Scroller(options);
scroll.init();

That’s all! hopefully, you have successfully integrated this smooth scroll to top code snippet into your project. If you have any questions or facing any issues, feel free to comment below.

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