interactjs/src/utils/arr.js

Drag and drop, resizing and multi-touch gestures with inertia and snapping for modern browsers (and also IE9+)

function contains (array, target) {
  return array.indexOf(target) !== -1;
}

function merge (target, source) {
  for (const item of source) {
    target.push(item);
  }

  return target;
}

module.exports = {
  contains,
  merge,
};