How to Add Smooth Scrolling Back To Top Button using react js?

Question

I have implemented this using jquery but want to create a component in react to do the same

<script>            
jQuery(document).ready(function() {
    var offset = 220;
    var duration = 500;
    jQuery(window).scroll(function() {
        if (jQuery(this).scrollTop() > offset) {
            jQuery('.move-top').fadeIn(duration);
        } else {
            jQuery('.move-top').fadeOut(duration);
        }
    });

    jQuery('.move-top').click(function(event) {
        event.preventDefault();
        jQuery('html, body').animate({scrollTop: 0}, duration);
        return false;
    })
});
</script>

In my page footer

<a href="#" class="move-top">↑</a>

Answer 1

First, we need to track the page as it's scrolled in the state of the component. This tracking should only be happening while the component is mounted. This can be done like so:

getInitialState: function() {
  return { scrollTop: 0 };
},
componentWillMount: function() {
  window.addEventListener('scroll', this.handleScroll);
},
componentWillUnmount: function() {
  window.removeEventListener('scroll', this.handleScroll);
},
handleScroll: function() {
   this.setState({scrollTop: $(window).scrollTop()});
},

Note: this is still using jQuery to get the current scroll position. See this question for doing this without jQuery.

Then we need to render the component:

scrollToTop: function() {
  $(window).animate({scrollTop: 0}, this.props.duration);
},
render: function() {
  if (this.state.scrollTop < this.props.offset) {
    return null;
  }

  return <a href="#" className="move-top" onClick={this.scrollToTop}>↑</a>
}

This is still using jQuery to do the actual scrolling. Have a look a this question for scrolling without jQuery.

If you want this component to fade in and out, you should wrap it in a ReactCSSTransitionGroup and use CSS animations. This is documented on the React docs.

Here's a JSFiddle demo.

Answer 2

If you'd like to avoid jQuery altogether

var Example = React.createClass({
    scrollUp: function () {
        var doc = document.documentElement;
        var top = (window.pageYOffset || doc.scrollTop) - (doc.clientTop || 0);

        if (top > 0) {
            window.scrollTo(0, top - 15)
            setTimeout(this.scrollUp, 10)
        }
    },
    render: function () {
        return (<div><h1>Page Header</h1>
            <div ref="container" className="container">
                <p>
                    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore
                    et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
                    aliquip ex ea commodo consequat. Duis aute irure dolor
                    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
                    occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
                </p>
                <p>
                    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore
                    et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
                    aliquip ex ea commodo consequat. Duis aute irure dolor
                    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
                    occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
                </p>
                <p>
                    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore
                    et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
                    aliquip ex ea commodo consequat. Duis aute irure dolor
                    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
                    occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
                </p>
                <p>
                    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore
                    et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
                    aliquip ex ea commodo consequat. Duis aute irure dolor
                    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
                    occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
                </p>
                <p>
                    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore
                    et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
                    aliquip ex ea commodo consequat. Duis aute irure dolor
                    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
                    occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
                </p>
                <p>
                    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore
                    et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
                    aliquip ex ea commodo consequat. Duis aute irure dolor
                    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
                    occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
                </p>
                <p>
                    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore
                    et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
                    aliquip ex ea commodo consequat. Duis aute irure dolor
                    in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
                    occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
                </p>

                <a className="move-top" onClick={this.scrollUp}>Up</a>
            </div>
        </div>);
    }
});