66 lines
1.8 KiB
JavaScript
66 lines
1.8 KiB
JavaScript
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( function() {
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'use strict';
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// Feature Test
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if ( 'querySelector' in document && 'addEventListener' in window ) {
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var goTopBtn = document.querySelector( '.generate-back-to-top' );
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var trackScroll = function() {
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var scrolled = window.pageYOffset;
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var coords = goTopBtn.getAttribute( 'data-start-scroll' );
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if ( scrolled > coords ) {
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goTopBtn.classList.add( 'generate-back-to-top__show' );
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}
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if ( scrolled < coords ) {
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goTopBtn.classList.remove( 'generate-back-to-top__show' );
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}
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};
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// Function to animate the scroll
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var smoothScroll = function( anchor, duration ) {
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// Calculate how far and how fast to scroll
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var startLocation = window.pageYOffset;
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var endLocation = document.body.offsetTop;
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var distance = endLocation - startLocation;
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var increments = distance / ( duration / 16 );
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var stopAnimation;
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// Scroll the page by an increment, and check if it's time to stop
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var animateScroll = function() {
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window.scrollBy( 0, increments );
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stopAnimation();
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};
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// Stop animation when you reach the anchor OR the top of the page
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stopAnimation = function() {
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var travelled = window.pageYOffset;
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if ( travelled <= ( endLocation || 0 ) ) {
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clearInterval( runAnimation );
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document.activeElement.blur();
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}
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};
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// Loop the animation function
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var runAnimation = setInterval( animateScroll, 16 );
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};
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if ( goTopBtn ) {
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// Show the button when scrolling down.
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window.addEventListener( 'scroll', trackScroll );
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// Scroll back to top when clicked.
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goTopBtn.addEventListener( 'click', function( e ) {
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e.preventDefault();
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if ( generatepressBackToTop.smooth ) {
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smoothScroll( document.body, goTopBtn.getAttribute( 'data-scroll-speed' ) || 400 );
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} else {
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window.scrollTo( 0, 0 );
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}
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}, false );
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}
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}
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}() );
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