Function copy

test/angular/1.7/angular.js:1009–1152

* @ngdoc function * @name angular.copy * @module ng * @kind function * * @description * Creates a deep copy of `source`, which should be an object or an array. This functions is used * internally, mostly in the change-detection code. It is not intended as an all-purpose copy * function, and

(source, destination, maxDepth)

  </example>
 */
function copy(source, destination, maxDepth) {
  var stackSource = [];
  var stackDest = [];
  maxDepth = isValidObjectMaxDepth(maxDepth) ? maxDepth : NaN;

  if (destination) {
    if (isTypedArray(destination) || isArrayBuffer(destination)) {
      throw ngMinErr('cpta', 'Can\'t copy! TypedArray destination cannot be mutated.');
    }
    if (source === destination) {
      throw ngMinErr('cpi', 'Can\'t copy! Source and destination are identical.');
    }

    // Empty the destination object
    if (isArray(destination)) {
      destination.length = 0;
    } else {
      forEach(destination, function(value, key) {
        if (key !== '$$hashKey') {
          delete destination[key];
        }
      });
    }

    stackSource.push(source);
    stackDest.push(destination);
    return copyRecurse(source, destination, maxDepth);
  }

  return copyElement(source, maxDepth);

  function copyRecurse(source, destination, maxDepth) {
    maxDepth--;
    if (maxDepth < 0) {
      return '...';
    }
    var h = destination.$$hashKey;
    var key;
    if (isArray(source)) {
      for (var i = 0, ii = source.length; i < ii; i++) {
        destination.push(copyElement(source[i], maxDepth));
      }
    } else if (isBlankObject(source)) {
      // createMap() fast path --- Safe to avoid hasOwnProperty check because prototype chain is empty
      for (key in source) {
        destination[key] = copyElement(source[key], maxDepth);
      }
    } else if (source && typeof source.hasOwnProperty === 'function') {
      // Slow path, which must rely on hasOwnProperty
      for (key in source) {
        if (source.hasOwnProperty(key)) {
          destination[key] = copyElement(source[key], maxDepth);
        }
      }
    } else {
      // Slowest path --- hasOwnProperty can't be called as a method
      for (key in source) {
        if (hasOwnProperty.call(source, key)) {