javascript - Angular 的 copy 函数，看不太懂，求分析下

Question

function copy(source, destination, stackSource, stackDest) {
  if (isWindow(source) || isScope(source)) {
    throw ngMinErr('cpws',
      "Can't copy! Making copies of Window or Scope instances is not supported.");
  }

  if (!destination) {
    destination = source;
    if (source) {
      if (isArray(source)) {
        destination = copy(source, [], stackSource, stackDest);
      } else if (isDate(source)) {
        destination = new Date(source.getTime());
      } else if (isRegExp(source)) {
        destination = new RegExp(source.source, source.toString().match(/[^\/]*$/)[0]);
        destination.lastIndex = source.lastIndex;
      } else if (isObject(source)) {
        destination = copy(source, {}, stackSource, stackDest);
      }
    }
  } else {
    if (source === destination) throw ngMinErr('cpi',
      "Can't copy! Source and destination are identical.");

    stackSource = stackSource || [];
    stackDest = stackDest || [];

    if (isObject(source)) {
      var index = indexOf(stackSource, source);
      if (index !== -1) return stackDest[index];

      stackSource.push(source);
      stackDest.push(destination);
    }

    var result;
    if (isArray(source)) {
      destination.length = 0;
      for ( var i = 0; i < source.length; i++) {
        result = copy(source[i], null, stackSource, stackDest);
        if (isObject(source[i])) {
          stackSource.push(source[i]);
          stackDest.push(result);
        }
        destination.push(result);
      }
    } else {
      var h = destination.$$hashKey;
      if (isArray(destination)) {
        destination.length = 0;
      } else {
        forEach(destination, function(value, key) {
          delete destination[key];
        });
      }
      for ( var key in source) {
        result = copy(source[key], null, stackSource, stackDest);
        if (isObject(source[key])) {
          stackSource.push(source[key]);
          stackDest.push(result);
        }
        destination[key] = result;
      }
      setHashKey(destination,h);
    }

  }
  return destination;
}

Answer 1

一般这么长的代码都不会有人看, 真的. 不信你等等看.

Answer 2

一般这么长的代码都不会有人看, 真的. 不信你等等看.

Answer 3

一般这么长的代码都不会有人看, 真的. 不信你等等看

Answer 4

一般这么长的代码都不会有人看, 真的. 不信你等等看.

Answer 5

一般这么长的代码都不会有人看, 真的. 不信你等等看

Answer 6

一般这么长的代码都不会有人看, 真的. 不信你等等看

Answer 7

一般这么长的代码都不会有人看, 真的. 不信你等等看.

Answer 8

一般这么长的代码都不会有人看, 真的. 不信你等等看

Answer 9

一般这么长的代码都不会有人看, 真的. 不信你等等看

Answer 10

一般这么长的代码都不会有人看, 真的. 不信你等等看.