dragscroll.js

/**
 * @fileoverview dragscroll-zoom - scroll area by dragging and zoom in~out
 * @version 1.0.1
 *
 * @license MIT, see https://github.com/vv2t/dragscroll-zoom
 * @copyright 2017 vv2t <vv2@tuta.io>
 *
 * This project began as a fork of dragscroll https://github.com/asvd/dragscroll
 */

(function(root, factory) {
  if (typeof define === 'function' && define.amd) {
    define(['exports'], factory);
  } else if (typeof exports !== 'undefined') {
    factory(exports);
  } else {
    factory((root.dragscroll = {}));
  }
})(this, function(exports) {
  var _window = window;
  var _document = document;
  var mousemove = 'mousemove';
  var mouseup = 'mouseup';
  var mousedown = 'mousedown';
  var EventListener = 'EventListener';
  var addEventListener = 'add' + EventListener;
  var removeEventListener = 'remove' + EventListener;
  var newScrollX, newScrollY;

  var dragged = [];
  var reset = function(i, el) {
    for (i = 0; i < dragged.length; ) {
      el = dragged[i++];
      el = el.container || el;
      el[removeEventListener](mousedown, el.md, 0);
      _window[removeEventListener](mouseup, el.mu, 0);
      _window[removeEventListener](mousemove, el.mm, 0);
    }

    // cloning into array since HTMLCollection is updated dynamically
    dragged = [].slice.call(_document.getElementsByClassName('dragscroll'));
    for (i = 0; i < dragged.length; ) {
      (function(el, lastClientX, lastClientY, pushed, scroller, cont) {
        (cont = el.container || el)[addEventListener](
          mousedown,
          (cont.md = function(e) {
            if (
              !el.hasAttribute('nochilddrag') ||
              _document.elementFromPoint(e.pageX, e.pageY) == cont
            ) {
              pushed = 1;
              lastClientX = e.clientX;
              lastClientY = e.clientY;

              e.preventDefault();
            }
          }),
          0,
        );

        _window[addEventListener](
          mouseup,
          (cont.mu = function() {
            pushed = 0;
          }),
          0,
        );

        _window[addEventListener](
          mousemove,
          (cont.mm = function(e) {
            if (pushed) {
              (scroller = el.scroller || el).scrollLeft -= newScrollX =
                -lastClientX + (lastClientX = e.clientX);
              scroller.scrollTop -= newScrollY =
                -lastClientY + (lastClientY = e.clientY);
              if (el == _document.body) {
                (scroller = _document.documentElement).scrollLeft -= newScrollX;
                scroller.scrollTop -= newScrollY;
              }
            }
          }),
          0,
        );
      })(dragged[i++]);
    }
  };

  if (_document.readyState == 'complete') {
    reset();
  } else {
    _window[addEventListener]('load', reset, 0);
  }

  exports.reset = reset;
});

function zoomIn(n) {
  var imgSize = document.getElementById('dragsimg').style.width;
  var zoom = Number(imgSize.replace(/[^0-9]/g, '')) + n;
  document.getElementById('dragsimg').style.width = zoom + '%';
}

function zoomOut(n) {
  var imgSize = document.getElementById('dragsimg').style.width;

  if (Number(imgSize.replace(/[^0-9]/g, '')) <= 100) {
    return false;
  }

  var zoom = Number(imgSize.replace(/[^0-9]/g, '')) - n;
  document.getElementById('dragsimg').style.width = zoom + '%';
}