rellax.js

// ------------------------------------------
// Rellax.js
// Buttery smooth parallax library
// Copyright (c) 2016 Moe Amaya (@moeamaya)
// MIT license
//
// Thanks to Paraxify.js and Jaime Cabllero
// for parallax concepts
// ------------------------------------------

(function (root, factory) {
  if (typeof define === 'function' && define.amd) {
    // AMD. Register as an anonymous module.
    define([], factory);
  } else if (typeof module === 'object' && module.exports) {
    // Node. Does not work with strict CommonJS, but
    // only CommonJS-like environments that support module.exports,
    // like Node.
    module.exports = factory();
  } else {
    // Browser globals (root is window)
    root.Rellax = factory();
  }
}(this, function () {
  var Rellax = function(el, options){
    "use strict";

    var self = Object.create(Rellax.prototype);

    var posY = 0;
    var screenY = 0;
    var posX = 0;
    var screenX = 0;
    var blocks = [];
    var pause = true;

    // check what requestAnimationFrame to use, and if
    // it's not supported, use the onscroll event
    var loop = window.requestAnimationFrame ||
      window.webkitRequestAnimationFrame ||
      window.mozRequestAnimationFrame ||
      window.msRequestAnimationFrame ||
      window.oRequestAnimationFrame ||
      function(callback){ setTimeout(callback, 1000 / 60); };

    // check which transform property to use
    var transformProp = window.transformProp || (function(){
        var testEl = document.createElement('div');
        if (testEl.style.transform === null) {
          var vendors = ['Webkit', 'Moz', 'ms'];
          for (var vendor in vendors) {
            if (testEl.style[ vendors[vendor] + 'Transform' ] !== undefined) {
              return vendors[vendor] + 'Transform';
            }
          }
        }
        return 'transform';
      })();

    // Default Settings
    self.options = {
      speed: -2,
      center: false,
      wrapper: null,
      relativeToWrapper: false,
      round: true,
      vertical: true,
      horizontal: false,
      callback: function() {},
    };

    // User defined options (might have more in the future)
    if (options){
      Object.keys(options).forEach(function(key){
        self.options[key] = options[key];
      });
    }

    // By default, rellax class
    if (!el) {
      el = '.rellax';
    }

    // check if el is a className or a node
    var elements = typeof el === 'string' ? document.querySelectorAll(el) : [el];

    // Now query selector
    if (elements.length > 0) {
      self.elems = elements;
    }

    // The elements don't exist
    else {
      throw new Error("The elements you're trying to select don't exist.");
    }

    // Has a wrapper and it exists
    if (self.options.wrapper) {
      if (!self.options.wrapper.nodeType) {
        var wrapper = document.querySelector(self.options.wrapper);

        if (wrapper) {
          self.options.wrapper = wrapper;
        } else {
          throw new Error("The wrapper you're trying to use don't exist.");
        }
      }
    }


    // Get and cache initial position of all elements
    var cacheBlocks = function() {
      for (var i = 0; i < self.elems.length; i++){
        var block = createBlock(self.elems[i]);
        blocks.push(block);
      }
    };


    // Let's kick this script off
    // Build array for cached element values
    var init = function() {
      for (var i = 0; i < blocks.length; i++){
        self.elems[i].style.cssText = blocks[i].style;
      }

      blocks = [];

      screenY = window.innerHeight;
      screenX = window.innerWidth;
      setPosition();

      cacheBlocks();

      // If paused, unpause and set listener for window resizing events
      if (pause) {
        window.addEventListener('resize', init);
        pause = false;
      }
      animate();
    };

    // We want to cache the parallax blocks'
    // values: base, top, height, speed
    // el: is dom object, return: el cache values
    var createBlock = function(el) {
      var dataPercentage = el.getAttribute( 'data-rellax-percentage' );
      var dataSpeed = el.getAttribute( 'data-rellax-speed' );
      var dataZindex = el.getAttribute( 'data-rellax-zindex' ) || 0;

      // initializing at scrollY = 0 (top of browser), scrollX = 0 (left of browser)
      // ensures elements are positioned based on HTML layout.
      //
      // If the element has the percentage attribute, the posY and posX needs to be
      // the current scroll position's value, so that the elements are still positioned based on HTML layout
      var wrapperPosY = self.options.wrapper ? self.options.wrapper.scrollTop : (window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop);
      // If the option relativeToWrapper is true, use the wrappers offset to top, subtracted from the current page scroll.
      if (self.options.relativeToWrapper) {
        var scrollPosY = (window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop);
        wrapperPosY = scrollPosY - self.options.wrapper.offsetTop;
      }
      var posY = self.options.vertical ? ( dataPercentage || self.options.center ? wrapperPosY : 0 ) : 0;
      var posX = self.options.horizontal ? ( dataPercentage || self.options.center ? (window.pageXOffset || document.documentElement.scrollLeft || document.body.scrollLeft) : 0 ) : 0;

      var blockTop = posY + el.getBoundingClientRect().top;
      var blockHeight = el.clientHeight || el.offsetHeight || el.scrollHeight;

      var blockLeft = posX + el.getBoundingClientRect().left;
      var blockWidth = el.clientWidth || el.offsetWidth || el.scrollWidth;

      // apparently parallax equation everyone uses
      var percentageY = dataPercentage ? dataPercentage : (posY - blockTop + screenY) / (blockHeight + screenY);
      var percentageX = dataPercentage ? dataPercentage : (posX - blockLeft + screenX) / (blockWidth + screenX);
      if(self.options.center){ percentageX = 0.5; percentageY = 0.5; }

      // Optional individual block speed as data attr, otherwise global speed
      var speed = dataSpeed ? dataSpeed : self.options.speed;

      var bases = updatePosition(percentageX, percentageY, speed);

      // ~~Store non-translate3d transforms~~
      // Store inline styles and extract transforms
      var style = el.style.cssText;
      var transform = '';

      // Check if there's an inline styled transform
      if (style.indexOf('transform') >= 0) {
        // Get the index of the transform
        var index = style.indexOf('transform');

        // Trim the style to the transform point and get the following semi-colon index
        var trimmedStyle = style.slice(index);
        var delimiter = trimmedStyle.indexOf(';');

        // Remove "transform" string and save the attribute
        if (delimiter) {
          transform = " " + trimmedStyle.slice(11, delimiter).replace(/\s/g,'');
        } else {
          transform = " " + trimmedStyle.slice(11).replace(/\s/g,'');
        }
      }

      return {
        baseX: bases.x,
        baseY: bases.y,
        top: blockTop,
        left: blockLeft,
        height: blockHeight,
        width: blockWidth,
        speed: speed,
        style: style,
        transform: transform,
        zindex: dataZindex
      };
    };

    // set scroll position (posY, posX)
    // side effect method is not ideal, but okay for now
    // returns true if the scroll changed, false if nothing happened
    var setPosition = function() {
      var oldY = posY;
      var oldX = posX;

      posY = self.options.wrapper ? self.options.wrapper.scrollTop : (document.documentElement || document.body.parentNode || document.body).scrollTop || window.pageYOffset;
      posX = self.options.wrapper ? self.options.wrapper.scrollLeft : (document.documentElement || document.body.parentNode || document.body).scrollLeft || window.pageXOffset;
      // If option relativeToWrapper is true, use relative wrapper value instead.
      if (self.options.relativeToWrapper) {
        var scrollPosY = (document.documentElement || document.body.parentNode || document.body).scrollTop || window.pageYOffset;
        posY = scrollPosY - self.options.wrapper.offsetTop;
      }


      if (oldY != posY && self.options.vertical) {
        // scroll changed, return true
        return true;
      }

      if (oldX != posX && self.options.horizontal) {
        // scroll changed, return true
        return true;
      }

      // scroll did not change
      return false;
    };

    // Ahh a pure function, gets new transform value
    // based on scrollPosition and speed
    // Allow for decimal pixel values
    var updatePosition = function(percentageX, percentageY, speed) {
      var result = {};
      var valueX = (speed * (100 * (1 - percentageX)));
      var valueY = (speed * (100 * (1 - percentageY)));

      result.x = self.options.round ? Math.round(valueX) : Math.round(valueX * 100) / 100;
      result.y = self.options.round ? Math.round(valueY) : Math.round(valueY * 100) / 100;

      return result;
    };

    // Loop
    var update = function() {
      if (setPosition() && pause === false) {
        animate();
      }

      // loop again
      loop(update);
    };

    // Transform3d on parallax element
    var animate = function() {
      var positions;
      for (var i = 0; i < self.elems.length; i++){
        var percentageY = ((posY - blocks[i].top + screenY) / (blocks[i].height + screenY));
        var percentageX = ((posX - blocks[i].left + screenX) / (blocks[i].width + screenX));

        // Subtracting initialize value, so element stays in same spot as HTML
        positions = updatePosition(percentageX, percentageY, blocks[i].speed);// - blocks[i].baseX;
        var positionY = positions.y - blocks[i].baseY;
        var positionX = positions.x - blocks[i].baseX;

        var zindex = blocks[i].zindex;

        // Move that element
        // (Set the new translation and append initial inline transforms.)
        var translate = 'translate3d(' + (self.options.horizontal ? positionX : '0') + 'px,' + (self.options.vertical ? positionY : '0') + 'px,' + zindex + 'px) ' + blocks[i].transform;
        self.elems[i].style[transformProp] = translate;
      }
      self.options.callback(positions);
    };

    self.destroy = function() {
      for (var i = 0; i < self.elems.length; i++){
        self.elems[i].style.cssText = blocks[i].style;
      }

      // Remove resize event listener if not pause, and pause
      if (!pause) {
        window.removeEventListener('resize', init);
        pause = true;
      }
    };

    // Init
    init();

    // Start the loop
    update();

    // Allow to recalculate the initial values whenever we want
    self.refresh = init;

    return self;
  };
  return Rellax;
}));