在Angular 2中复制对象的最佳方法是什么？

Question

Angular 1.x has methods on the global angular object like angular.copy, angular.shallowCopy (not to mention others like angular.forEach) that don't seem to have an equivalent version in Angular 2. Perhaps it is just not documented. If Angular 2 doesn't intend on providing these utils, what is the best way to get that functionality?

I know I could roll my own shallow copy method using the logic from angular 1.x:

function shallowCopy(src, dst) {
  if (isArray(src)) {
    dst = dst || [];

    for (var i = 0, ii = src.length; i < ii; i++) {
      dst[i] = src[i];
    }
  } else if (isObject(src)) {
    dst = dst || {};

    for (var key in src) {
      if (!(key.charAt(0) === '$' && key.charAt(1) === '$')) {
        dst[key] = src[key];
      }
    }
  }

  return dst || src;
}

But the deep copy logic is much more complicated (obviously)

Answer 1

When the object is an array , I use:

copyOfArray = originalArray.slice(0, originalArray.length);

Where originalArray is the original array object.

The built-in javascript array.slice(start, end) function returns a subset of the array as a new array object ( JavaScript Array slice() Method ). Setting the start and end boundaries to the size of the original array returns a copy of the whole array.

Answer 2

Why not simply duplicate the angular 1 copy function ?

From the sources ( need to adapt some stuff like the calls to error handlers, but basically : )

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 (isTypedArray(destination)) {
    throw ngMinErr('cpta',
      "Can't copy! TypedArray destination cannot be mutated.");
  }

  if (!destination) {
    destination = source;
    if (isObject(source)) {
      var index;
      if (stackSource && (index = stackSource.indexOf(source)) !== -1) {
        return stackDest[index];
      }

      // TypedArray, Date and RegExp have specific copy functionality and must be
      // pushed onto the stack before returning.
      // Array and other objects create the base object and recurse to copy child
      // objects. The array/object will be pushed onto the stack when recursed.
      if (isArray(source)) {
        return copy(source, [], stackSource, stackDest);
      } else if (isTypedArray(source)) {
        destination = new source.constructor(source);
      } 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 (isFunction(source.cloneNode)) {
          destination = source.cloneNode(true);
      } else {
        var emptyObject = Object.create(getPrototypeOf(source));
        return copy(source, emptyObject, stackSource, stackDest);
      }

      if (stackDest) {
        stackSource.push(source);
        stackDest.push(destination);
      }
    }
  } else {
    if (source === destination) throw ngMinErr('cpi',
      "Can't copy! Source and destination are identical.");

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

    if (isObject(source)) {
      stackSource.push(source);
      stackDest.push(destination);
    }

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