Function patchClass

packages/zone.js/lib/common/utils.ts:323–392

(className: string)

// wrap some native API on `window`
export function patchClass(className: string) {
  const OriginalClass = _global[className];
  if (!OriginalClass) return;
  // keep original class in global
  _global[zoneSymbol(className)] = OriginalClass;

  _global[className] = function () {
    const a = bindArguments(<any>arguments, className);
    switch (a.length) {
      case 0:
        this[originalInstanceKey] = new OriginalClass();
        break;
      case 1:
        this[originalInstanceKey] = new OriginalClass(a[0]);
        break;
      case 2:
        this[originalInstanceKey] = new OriginalClass(a[0], a[1]);
        break;
      case 3:
        this[originalInstanceKey] = new OriginalClass(a[0], a[1], a[2]);
        break;
      case 4:
        this[originalInstanceKey] = new OriginalClass(a[0], a[1], a[2], a[3]);
        break;
      default:
        throw new Error('Arg list too long.');
    }
  };

  // attach original delegate to patched function
  attachOriginToPatched(_global[className], OriginalClass);

  const instance = new OriginalClass(function () {});

  let prop;
  for (prop in instance) {
    // https://bugs.webkit.org/show_bug.cgi?id=44721
    if (className === 'XMLHttpRequest' && prop === 'responseBlob') continue;
    (function (prop) {
      if (typeof instance[prop] === 'function') {
        _global[className].prototype[prop] = function () {
          return this[originalInstanceKey][prop].apply(this[originalInstanceKey], arguments);
        };
      } else {
        ObjectDefineProperty(_global[className].prototype, prop, {
          set: function (fn) {
            if (typeof fn === 'function') {
              this[originalInstanceKey][prop] = wrapWithCurrentZone(fn, className + '.' + prop);
              // keep callback in wrapped function so we can
              // use it in Function.prototype.toString to return
              // the native one.
              attachOriginToPatched(this[originalInstanceKey][prop], fn);
            } else {
              this[originalInstanceKey][prop] = fn;
            }
          },
          get: function () {
            return this[originalInstanceKey][prop];