sveltfy/src/actions/Jump/jump.js

A material design framework/component library for Svelte, with full support for light and dark themes and customisability.

/* eslint-disable */
// Robert Penner's easeInOutQuad

// find the rest of his easing functions here: http://robertpenner.com/easing/
// find them exported for ES6 consumption here: https://github.com/jaxgeller/ez.js

var easeInOutQuad = function easeInOutQuad(t, b, c, d) {
  t /= d / 2;
  if (t < 1) return (c / 2) * t * t + b;
  t--;
  return (-c / 2) * (t * (t - 2) - 1) + b;
};

var _typeof =
  typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol'
    ? function (obj) {
        return typeof obj;
      }
    : function (obj) {
        return obj &&
          typeof Symbol === 'function' &&
          obj.constructor === Symbol &&
          obj !== Symbol.prototype
          ? 'symbol'
          : typeof obj;
      };

var jumper = function jumper() {
  // private variable cache
  // no variables are created during a jump, preventing memory leaks

  var element = void 0; // element to scroll to                   (node)

  var start = void 0; // where scroll starts                    (px)
  var stop = void 0; // where scroll stops                     (px)

  var offset = void 0; // adjustment from the stop position      (px)
  var easing = void 0; // easing function                        (function)
  var a11y = void 0; // accessibility support flag             (boolean)

  var distance = void 0; // distance of scroll                     (px)
  var duration = void 0; // scroll duration                        (ms)

  var timeStart = void 0; // time scroll started                    (ms)
  var timeElapsed = void 0; // time spent scrolling thus far          (ms)

  var next = void 0; // next scroll position                   (px)

  var callback = void 0; // to call when done scrolling            (function)

  // scroll position helper

  function location() {
    return window.scrollY || window.pageYOffset;
  }

  // element offset helper

  function top(element) {
    return element.getBoundingClientRect().top + start;
  }

  // rAF loop helper

  function loop(timeCurrent) {
    // store time scroll started, if not started already
    if (!timeStart) {
      timeStart = timeCurrent;
    }

    // determine time spent scrolling so far
    timeElapsed = timeCurrent - timeStart;

    // calculate next scroll position
    next = easing(timeElapsed, start, distance, duration);

    // scroll to it
    window.scrollTo(0, next);

    // check progress
    timeElapsed < duration
      ? window.requestAnimationFrame(loop) // continue scroll loop
      : done(); // scrolling is done
  }

  // scroll finished helper

  function done() {
    // account for rAF time rounding inaccuracies
    window.scrollTo(0, start + distance);

    // if scrolling to an element, and accessibility is enabled
    if (element && a11y) {
      // add tabindex indicating programmatic focus
      element.setAttribute('tabindex', '-1');

      // focus the element
      element.focus();
    }

    // if it exists, fire the callback
    if (typeof callback === 'function') {
      callback();
    }

    // reset time for next jump
    timeStart = false;
  }

  // API

  function jump(target) {
    var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};

    // resolve options, or use defaults
    duration = options.duration || 1000;
    offset = options.offset || 0;
    callback = options.callback; // "undefined" is a suitable default, and won't be called
    easing = options.easing || easeInOutQuad;
    a11y = options.a11y || false;

    // cache starting position
    start = location();

    // resolve target
    switch (typeof target === 'undefined' ? 'undefined' : _typeof(target)) {
      // scroll from current position
      case 'number':
        element = undefined; // no element to scroll to
        a11y = false; // make sure accessibility is off
        stop = start + target;
        break;

      // scroll to element (node)
      // bounding rect is relative to the viewport
      case 'object':
        element = target;
        stop = top(element);
        break;

      // scroll to element (selector)
      // bounding rect is relative to the viewport
      case 'string':
        element = document.querySelector(target);
        stop = top(element);
        break;
    }

    // resolve scroll distance, accounting for offset
    distance = stop - start + offset;

    // resolve duration
    switch (_typeof(options.duration)) {
      // number in ms
      case 'number':
        duration = options.duration;
        break;

      // function passed the distance of the scroll
      case 'function':
        duration = options.duration(distance);
        break;
    }

    // start the loop
    window.requestAnimationFrame(loop);
  }

  // expose only the jump method
  return jump;
};

// export singleton

var singleton = jumper();

export default singleton;