bidiu

/**
 * @param {string} postCode post code
 * @return {string|null}
 *      post code after an attempt converting to canonical format, 
 *      in case conversion cannot be made, null will be returned.
 */
function convertPostCode(postCode) {
  if (!postCode || typeof postCode !== 'string') {
    // postCode is null, undefined, or non string
    return null;

bidiu

class RangeIterable {
    constructor(start, end, step) {
        this.start = start;
        this.end = end;
        this.step = step;
        this.cnt = start;
    }

    [Symbol.iterator]() {
        return this;

bidiu

function Promise(func) {
  var state = 'pending';
  var deferred = null; // the "then" handler
  var value;

  function resolve(newValue) {
    state = 'resolved';
    value = newValue;
    if (deferred) {
      handle(deferred);

bidiu

// could be replaced by getBoundingClientRect()
function getDistanceToViewport(element: HTMLElement) {
  let left = 0, top = 0, current: HTMLElement

  current = element
  while (current) {
    left += current.offsetLeft
    top += current.offsetTop
    current = current.offsetParent as HTMLElement
  }