interactjs/src/utils/index.js

Drag and drop, resizing and multi-touch gestures with inertia and snapping for modern browsers (and also IE8+)

const extend = require('./extend');
const win    = require('./window');

const utils = {
  warnOnce: function (method, message) {
    let warned = false;

    return function () {
      if (!warned) {
        win.window.console.warn(message);
        warned = true;
      }

      return method.apply(this, arguments);
    };
  },

  // http://stackoverflow.com/a/5634528/2280888
  _getQBezierValue: function (t, p1, p2, p3) {
    const iT = 1 - t;
    return iT * iT * p1 + 2 * iT * t * p2 + t * t * p3;
  },

  getQuadraticCurvePoint: function (startX, startY, cpX, cpY, endX, endY, position) {
    return {
      x:  utils._getQBezierValue(position, startX, cpX, endX),
      y:  utils._getQBezierValue(position, startY, cpY, endY),
    };
  },

  // http://gizma.com/easing/
  easeOutQuad: function (t, b, c, d) {
    t /= d;
    return -c * t*(t-2) + b;
  },

  copyAction: function (dest, src) {
    dest.name  = src.name;
    dest.axis  = src.axis;
    dest.edges = src.edges;

    return dest;
  },

  is         : require('./is'),
  extend     : extend,
  hypot      : require('./hypot'),
  getOriginXY: require('./getOriginXY'),
};

extend(utils, require('./arr'));
extend(utils, require('./domUtils'));
extend(utils, require('./pointerUtils'));
extend(utils, require('./rect'));

module.exports = utils;