面试时，深拷贝这个问题是常考的。涉及的面很广，比如 node 端怎么拷贝 buffer，而浏览器端是没有 buffer 的。如果仅仅是回答使用 JSON.stringify JSON.parse 应该是不能及格的。我们先来看看 lodash 写一个可以打 90 分的深拷贝做了哪些工作。
- 如果对象有环状的循环引用，怎么解决？
- /d/g.exec(‘dd’)，这样正则执行返回的数组怎么拷贝？
/** Used as the size to enable large array optimizations. */
var LARGE_ARRAY_SIZE = 200;
/** Used to stand-in for `undefined` hash values. */
var HASH_UNDEFINED = '__lodash_hash_undefined__';
/** Used as references for various `Number` constants. */
var MAX_SAFE_INTEGER = 9007199254740991;
/** `Object#toString` result references. */
var argsTag = '[object Arguments]',
arrayTag = '[object Array]',
boolTag = '[object Boolean]',
dateTag = '[object Date]',
errorTag = '[object Error]',
funcTag = '[object Function]',
genTag = '[object GeneratorFunction]',
mapTag = '[object Map]',
numberTag = '[object Number]',
objectTag = '[object Object]',
promiseTag = '[object Promise]',
regexpTag = '[object RegExp]',
setTag = '[object Set]',
stringTag = '[object String]',
symbolTag = '[object Symbol]',
weakMapTag = '[object WeakMap]';
var arrayBufferTag = '[object ArrayBuffer]',
dataViewTag = '[object DataView]',
float32Tag = '[object Float32Array]',
float64Tag = '[object Float64Array]',
int8Tag = '[object Int8Array]',
int16Tag = '[object Int16Array]',
int32Tag = '[object Int32Array]',
uint8Tag = '[object Uint8Array]',
uint8ClampedTag = '[object Uint8ClampedArray]',
uint16Tag = '[object Uint16Array]',
uint32Tag = '[object Uint32Array]';
/**
* Used to match `RegExp`
* [syntax characters](http://ecma-international.org/ecma-262/7.0/#sec-patterns).
*/
var reRegExpChar = /[\\^$.*+?()[\]{}|]/g;
/** Used to match `RegExp` flags from their coerced string values. */
var reFlags = /\w*$/;
/** Used to detect host constructors (Safari). */
var reIsHostCtor = /^\[object .+?Constructor\]$/;
/** Used to detect unsigned integer values. */
var reIsUint = /^(?:0|[1-9]\d*)$/;
/** Used to identify `toStringTag` values supported by `_.clone`. */
var cloneableTags = {};
cloneableTags[argsTag] = cloneableTags[arrayTag] =
cloneableTags[arrayBufferTag] = cloneableTags[dataViewTag] =
cloneableTags[boolTag] = cloneableTags[dateTag] =
cloneableTags[float32Tag] = cloneableTags[float64Tag] =
cloneableTags[int8Tag] = cloneableTags[int16Tag] =
cloneableTags[int32Tag] = cloneableTags[mapTag] =
cloneableTags[numberTag] = cloneableTags[objectTag] =
cloneableTags[regexpTag] = cloneableTags[setTag] =
cloneableTags[stringTag] = cloneableTags[symbolTag] =
cloneableTags[uint8Tag] = cloneableTags[uint8ClampedTag] =
cloneableTags[uint16Tag] = cloneableTags[uint32Tag] = true;
cloneableTags[errorTag] = cloneableTags[funcTag] =
cloneableTags[weakMapTag] = false;
/** Detect free variable `global` from Node.js. */
var freeGlobal = typeof global == 'object' && global && global.Object === Object && global;
/** Detect free variable `self`. */
var freeSelf = typeof self == 'object' && self && self.Object === Object && self;
/** Used as a reference to the global object. */
var root = freeGlobal || freeSelf || Function('return this')();
/** Detect free variable `exports`. */
var freeExports = typeof exports == 'object' && exports && !exports.nodeType && exports;
/** Detect free variable `module`. */
var freeModule = freeExports && typeof module == 'object' && module && !module.nodeType && module;
/** Detect the popular CommonJS extension `module.exports`. */
var moduleExports = freeModule && freeModule.exports === freeExports;
/**
* Adds the key-value `pair` to `map`.
*
* @private
* @param {Object} map The map to modify.
* @param {Array} pair The key-value pair to add.
* @returns {Object} Returns `map`.
*/
function addMapEntry(map, pair) {
// Don't return `map.set` because it's not chainable in IE 11.
map.set(pair[0], pair[1]);
return map;
}
/**
* Adds `value` to `set`.
*
* @private
* @param {Object} set The set to modify.
* @param {*} value The value to add.
* @returns {Object} Returns `set`.
*/
function addSetEntry(set, value) {
// Don't return `set.add` because it's not chainable in IE 11.
set.add(value);
return set;
}
/**
* Appends the elements of `values` to `array`.
*
* @private
* @param {Array} array The array to modify.
* @param {Array} values The values to append.
* @returns {Array} Returns `array`.
*/
function arrayPush(array, values) {
var index = -1,
length = values.length,
offset = array.length;
while (++index < length) {
array[offset + index] = values[index];
}
return array;
}
/**
* A specialized version of `_.reduce` for arrays without support for
* iteratee shorthands.
*
* @private
* @param {Array} [array] The array to iterate over.
* @param {Function} iteratee The function invoked per iteration.
* @param {*} [accumulator] The initial value.
* @param {boolean} [initAccum] Specify using the first element of `array` as
* the initial value.
* @returns {*} Returns the accumulated value.
*/
function arrayReduce(array, iteratee, accumulator, initAccum) {
var index = -1,
length = array ? array.length : 0;
if (initAccum && length) {
accumulator = array[++index];
}
while (++index < length) {
accumulator = iteratee(accumulator, array[index], index, array);
}
return accumulator;
}
/**
* The base implementation of `_.times` without support for iteratee shorthands
* or max array length checks.
*
* @private
* @param {number} n The number of times to invoke `iteratee`.
* @param {Function} iteratee The function invoked per iteration.
* @returns {Array} Returns the array of results.
*/
function baseTimes(n, iteratee) {
var index = -1,
result = Array(n);
while (++index < n) {
result[index] = iteratee(index);
}
return result;
}
/**
* Gets the value at `key` of `object`.
*
* @private
* @param {Object} [object] The object to query.
* @param {string} key The key of the property to get.
* @returns {*} Returns the property value.
*/
function getValue(object, key) {
return object == null ? undefined : object[key];
}
/**
* Checks if `value` is a host object in IE < 9.
*
* @private
* @param {*} value The value to check.
* @returns {boolean} Returns `true` if `value` is a host object, else `false`.
*/
function isHostObject(value) {
// Many host objects are `Object` objects that can coerce to strings
// despite having improperly defined `toString` methods.
var result = false;
if (value != null && typeof value.toString != 'function') {
try {
result = !!(value + '');
} catch (e) {}
}
return result;
}
/**
* Converts `map` to its key-value pairs.
*
* @private
* @param {Object} map The map to convert.
* @returns {Array} Returns the key-value pairs.
*/
function mapToArray(map) {
var index = -1,
result = Array(map.size);
map.forEach(function(value, key) {
result[++index] = [key, value];
});
return result;
}
/**
* Creates a unary function that invokes `func` with its argument transformed.
*
* @private
* @param {Function} func The function to wrap.
* @param {Function} transform The argument transform.
* @returns {Function} Returns the new function.
*/
function overArg(func, transform) {
return function(arg) {
return func(transform(arg));
};
}
/**
* Converts `set` to an array of its values.
*
* @private
* @param {Object} set The set to convert.
* @returns {Array} Returns the values.
*/
function setToArray(set) {
var index = -1,
result = Array(set.size);
set.forEach(function(value) {
result[++index] = value;
});
return result;
}
/** Used for built-in method references. */
var arrayProto = Array.prototype,
funcProto = Function.prototype,
objectProto = Object.prototype;
/** Used to detect overreaching core-js shims. */
var coreJsData = root['__core-js_shared__'];
/** Used to detect methods masquerading as native. */
var maskSrcKey = (function() {
var uid = /[^.]+$/.exec(coreJsData && coreJsData.keys && coreJsData.keys.IE_PROTO || '');
return uid ? ('Symbol(src)_1.' + uid) : '';
}());
/** Used to resolve the decompiled source of functions. */
var funcToString = funcProto.toString;
/** Used to check objects for own properties. */
var hasOwnProperty = objectProto.hasOwnProperty;
/**
* Used to resolve the
* [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)
* of values.
*/
var objectToString = objectProto.toString;
/** Used to detect if a method is native. */
var reIsNative = RegExp('^' +
funcToString.call(hasOwnProperty).replace(reRegExpChar, '\\$&')
.replace(/hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
);
/** Built-in value references. */
var Buffer = moduleExports ? root.Buffer : undefined,
Symbol = root.Symbol,
Uint8Array = root.Uint8Array,
getPrototype = overArg(Object.getPrototypeOf, Object),
objectCreate = Object.create,
propertyIsEnumerable = objectProto.propertyIsEnumerable,
splice = arrayProto.splice;
/* Built-in method references for those with the same name as other `lodash` methods. */
var nativeGetSymbols = Object.getOwnPropertySymbols,
nativeKeys = overArg(Object.keys, Object);
/* Built-in method references that are verified to be native. */
var DataView = getNative(root, 'DataView'),
Map = getNative(root, 'Map'),
Promise = getNative(root, 'Promise'),
Set = getNative(root, 'Set'),
WeakMap = getNative(root, 'WeakMap'),
nativeCreate = getNative(Object, 'create');
/** Used to detect maps, sets, and weakmaps. */
var dataViewCtorString = toSource(DataView),
mapCtorString = toSource(Map),
promiseCtorString = toSource(Promise),
setCtorString = toSource(Set),
weakMapCtorString = toSource(WeakMap);
/** Used to convert symbols to primitives and strings. */
var symbolProto = Symbol ? Symbol.prototype : undefined,
symbolValueOf = symbolProto ? symbolProto.valueOf : undefined;
/**
* Creates a hash object.
*
* @private
* @constructor
* @param {Array} [entries] The key-value pairs to cache.
*/
function Hash(entries) {
var index = -1,
length = entries ? entries.length : 0;
this.clear();
while (++index < length) {
var entry = entries[index];
this.set(entry[0], entry[1]);
}
}
/**
* Removes all key-value entries from the hash.
*
* @private
* @name clear
* @memberOf Hash
*/
function hashClear() {
this.__data__ = nativeCreate ? nativeCreate(null) : {};
}
/**
* Removes `key` and its value from the hash.
*
* @private
* @name delete
* @memberOf Hash
* @param {Object} hash The hash to modify.
* @param {string} key The key of the value to remove.
* @returns {boolean} Returns `true` if the entry was removed, else `false`.
*/
function hashDelete(key) {
return this.has(key) && delete this.__data__[key];
}
/**
* Gets the hash value for `key`.
*
* @private
* @name get
* @memberOf Hash
* @param {string} key The key of the value to get.
* @returns {*} Returns the entry value.
*/
function hashGet(key) {
var data = this.__data__;
if (nativeCreate) {
var result = data[key];
return result === HASH_UNDEFINED ? undefined : result;
}
return hasOwnProperty.call(data, key) ? data[key] : undefined;
}
/**
* Checks if a hash value for `key` exists.
*
* @private
* @name has
* @memberOf Hash
* @param {string} key The key of the entry to check.
* @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
*/
function hashHas(key) {
var data = this.__data__;
return nativeCreate ? data[key] !== undefined : hasOwnProperty.call(data, key);
}
/**
* Sets the hash `key` to `value`.
*
* @private
* @name set
* @memberOf Hash
* @param {string} key The key of the value to set.
* @param {*} value The value to set.
* @returns {Object} Returns the hash instance.
*/
function hashSet(key, value) {
var data = this.__data__;
data[key] = (nativeCreate && value === undefined) ? HASH_UNDEFINED : value;
return this;
}
// Add methods to `Hash`.
Hash.prototype.clear = hashClear;
Hash.prototype['delete'] = hashDelete;
Hash.prototype.get = hashGet;
Hash.prototype.has = hashHas;
Hash.prototype.set = hashSet;
/**
* Creates an list cache object.
*
* @private
* @constructor
* @param {Array} [entries] The key-value pairs to cache.
*/
function ListCache(entries) {
var index = -1,
length = entries ? entries.length : 0;
this.clear();
while (++index < length) {
var entry = entries[index];
this.set(entry[0], entry[1]);
}
}
/**
* Removes all key-value entries from the list cache.
*
* @private
* @name clear
* @memberOf ListCache
*/
function listCacheClear() {
this.__data__ = [];
}
/**
* Removes `key` and its value from the list cache.
*
* @private
* @name delete
* @memberOf ListCache
* @param {string} key The key of the value to remove.
* @returns {boolean} Returns `true` if the entry was removed, else `false`.
*/
function listCacheDelete(key) {
var data = this.__data__,
index = assocIndexOf(data, key);
if (index < 0) {
return false;
}
var lastIndex = data.length - 1;
if (index == lastIndex) {
data.pop();
} else {
splice.call(data, index, 1);
}
return true;
}
/**
* Gets the list cache value for `key`.
*
* @private
* @name get
* @memberOf ListCache
* @param {string} key The key of the value to get.
* @returns {*} Returns the entry value.
*/
function listCacheGet(key) {
var data = this.__data__,
index = assocIndexOf(data, key);
return index < 0 ? undefined : data[index][1];
}
/**
* Checks if a list cache value for `key` exists.
*
* @private
* @name has
* @memberOf ListCache
* @param {string} key The key of the entry to check.
* @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
*/
function listCacheHas(key) {
return assocIndexOf(this.__data__, key) > -1;
}
/**
* Sets the list cache `key` to `value`.
*
* @private
* @name set
* @memberOf ListCache
* @param {string} key The key of the value to set.
* @param {*} value The value to set.
* @returns {Object} Returns the list cache instance.
*/
function listCacheSet(key, value) {
var data = this.__data__,
index = assocIndexOf(data, key);
if (index < 0) {
data.push([key, value]);
} else {
data[index][1] = value;
}
return this;
}
// Add methods to `ListCache`.
ListCache.prototype.clear = listCacheClear;
ListCache.prototype['delete'] = listCacheDelete;
ListCache.prototype.get = listCacheGet;
ListCache.prototype.has = listCacheHas;
ListCache.prototype.set = listCacheSet;
/**
* Creates a map cache object to store key-value pairs.
*
* @private
* @constructor
* @param {Array} [entries] The key-value pairs to cache.
*/
function MapCache(entries) {
var index = -1,
length = entries ? entries.length : 0;
this.clear();
while (++index < length) {
var entry = entries[index];
this.set(entry[0], entry[1]);
}
}
/**
* Removes all key-value entries from the map.
*
* @private
* @name clear
* @memberOf MapCache
*/
function mapCacheClear() {
this.__data__ = {
'hash': new Hash,
'map': new (Map || ListCache),
'string': new Hash
};
}
/**
* Removes `key` and its value from the map.
*
* @private
* @name delete
* @memberOf MapCache
* @param {string} key The key of the value to remove.
* @returns {boolean} Returns `true` if the entry was removed, else `false`.
*/
function mapCacheDelete(key) {
return getMapData(this, key)['delete'](key);
}
/**
* Gets the map value for `key`.
*
* @private
* @name get
* @memberOf MapCache
* @param {string} key The key of the value to get.
* @returns {*} Returns the entry value.
*/
function mapCacheGet(key) {
return getMapData(this, key).get(key);
}
/**
* Checks if a map value for `key` exists.
*
* @private
* @name has
* @memberOf MapCache
* @param {string} key The key of the entry to check.
* @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
*/
function mapCacheHas(key) {
return getMapData(this, key).has(key);
}
/**
* Sets the map `key` to `value`.
*
* @private
* @name set
* @memberOf MapCache
* @param {string} key The key of the value to set.
* @param {*} value The value to set.
* @returns {Object} Returns the map cache instance.
*/
function mapCacheSet(key, value) {
getMapData(this, key).set(key, value);
return this;
}
// Add methods to `MapCache`.
MapCache.prototype.clear = mapCacheClear;
MapCache.prototype['delete'] = mapCacheDelete;
MapCache.prototype.get = mapCacheGet;
MapCache.prototype.has = mapCacheHas;
MapCache.prototype.set = mapCacheSet;
/**
* Creates a stack cache object to store key-value pairs.
*
* @private
* @constructor
* @param {Array} [entries] The key-value pairs to cache.
*/
function Stack(entries) {
this.__data__ = new ListCache(entries);
}
/**
* Removes all key-value entries from the stack.
*
* @private
* @name clear
* @memberOf Stack
*/
function stackClear() {
this.__data__ = new ListCache;
}
/**
* Removes `key` and its value from the stack.
*
* @private
* @name delete
* @memberOf Stack
* @param {string} key The key of the value to remove.
* @returns {boolean} Returns `true` if the entry was removed, else `false`.
*/
function stackDelete(key) {
return this.__data__['delete'](key);
}
/**
* Gets the stack value for `key`.
*
* @private
* @name get
* @memberOf Stack
* @param {string} key The key of the value to get.
* @returns {*} Returns the entry value.
*/
function stackGet(key) {
return this.__data__.get(key);
}
/**
* Checks if a stack value for `key` exists.
*
* @private
* @name has
* @memberOf Stack
* @param {string} key The key of the entry to check.
* @returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
*/
function stackHas(key) {
return this.__data__.has(key);
}
/**
* Sets the stack `key` to `value`.
*
* @private
* @name set
* @memberOf Stack
* @param {string} key The key of the value to set.
* @param {*} value The value to set.
* @returns {Object} Returns the stack cache instance.
*/
function stackSet(key, value) {
var cache = this.__data__;
if (cache instanceof ListCache) {
var pairs = cache.__data__;
if (!Map || (pairs.length < LARGE_ARRAY_SIZE - 1)) {
pairs.push([key, value]);
return this;
}
cache = this.__data__ = new MapCache(pairs);
}
cache.set(key, value);
return this;
}
// Add methods to `Stack`.
Stack.prototype.clear = stackClear;
Stack.prototype['delete'] = stackDelete;
Stack.prototype.get = stackGet;
Stack.prototype.has = stackHas;
Stack.prototype.set = stackSet;
/**
* Creates an array of the enumerable property names of the array-like `value`.
*
* @private
* @param {*} value The value to query.
* @param {boolean} inherited Specify returning inherited property names.
* @returns {Array} Returns the array of property names.
*/
function arrayLikeKeys(value, inherited) {
// Safari 8.1 makes `arguments.callee` enumerable in strict mode.
// Safari 9 makes `arguments.length` enumerable in strict mode.
var result = (isArray(value) || isArguments(value))
? baseTimes(value.length, String)
: [];
var length = result.length,
skipIndexes = !!length;
for (var key in value) {
if ((inherited || hasOwnProperty.call(value, key)) &&
!(skipIndexes && (key == 'length' || isIndex(key, length)))) {
result.push(key);
}
}
return result;
}
/**
* Assigns `value` to `key` of `object` if the existing value is not equivalent
* using [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
* for equality comparisons.
*
* @private
* @param {Object} object The object to modify.
* @param {string} key The key of the property to assign.
* @param {*} value The value to assign.
*/
function assignValue(object, key, value) {
var objValue = object[key];
if (!(hasOwnProperty.call(object, key) && eq(objValue, value)) ||
(value === undefined && !(key in object))) {
object[key] = value;
}
}
/**
* Gets the index at which the `key` is found in `array` of key-value pairs.
*
* @private
* @param {Array} array The array to inspect.
* @param {*} key The key to search for.
* @returns {number} Returns the index of the matched value, else `-1`.
*/
function assocIndexOf(array, key) {
var length = array.length;
while (length--) {
if (eq(array[length][0], key)) {
return length;
}
}
return -1;
}
/**
* The base implementation of `_.assign` without support for multiple sources
* or `customizer` functions.
*
* @private
* @param {Object} object The destination object.
* @param {Object} source The source object.
* @returns {Object} Returns `object`.
*/
function baseAssign(object, source) {
return object && copyObject(source, keys(source), object);
}
/**
*
* @private
* @param {*} value The value to clone.
* @param {boolean} [isDeep] Specify a deep clone.
* @param {boolean} [isFull] Specify a clone including symbols.
* @param {Function} [customizer] The function to customize cloning.
* @param {string} [key] The key of `value`.
* @param {Object} [object] The parent object of `value`.
* @param {Object} [stack] Tracks traversed objects and their clone counterparts.
* @returns {*} Returns the cloned value.
*/
function baseClone(value, isDeep, isFull) {
var result;
if (!isObject(value)) {
return value;
}
var isArr = Array.isArray(value);
if (isArr) {
result = new Array(value.length);
} else {
var tag = getTag(value),
isFunc = tag == funcTag || tag == genTag;
if (tag == objectTag || tag == argsTag || isFunc) {
if (isHostObject(value)) {
return object ? value : {};
}
result = initCloneObject(isFunc ? {} : value);
if (!isDeep) {
return copySymbols(value, baseAssign(result, value));
}
} else {
if (!cloneableTags[tag]) {
return object ? value : {};
}
result = initCloneByTag(value, tag, baseClone, isDeep);
}
}
// Check for circular references and return its corresponding clone.
var stack = new Stack;
var stacked = stack.get(value);
if (stacked) {
return stacked;
}
stack.set(value, result);
if (!isArr) {
var props = isFull ? getAllKeys(value) : keys(value);
}
let arrZ = (props || value)
let len = arrZ.length
for(let i = 0; i < len; i++) {
let subValue = arrZ[i]
let key = i
if (props) {
key = subValue;
subValue = value[key];
}
// Recursively populate clone (susceptible to call stack limits).
assignValue(result, key, baseClone(subValue, isDeep, isFull));
}
return result;
}
/**
* The base implementation of `_.create` without support for assigning
* properties to the created object.
*
* @private
* @param {Object} prototype The object to inherit from.
* @returns {Object} Returns the new object.
*/
function baseCreate(proto) {
return isObject(proto) ? objectCreate(proto) : {};
}
/**
* The base implementation of `getAllKeys` and `getAllKeysIn` which uses
* `keysFunc` and `symbolsFunc` to get the enumerable property names and
* symbols of `object`.
*
* @private
* @param {Object} object The object to query.
* @param {Function} keysFunc The function to get the keys of `object`.
* @param {Function} symbolsFunc The function to get the symbols of `object`.
* @returns {Array} Returns the array of property names and symbols.
*/
function baseGetAllKeys(object, keysFunc, symbolsFunc) {
var result = keysFunc(object);
return Array.isArray(object) ? result : arrayPush(result, symbolsFunc(object));
}
/**
* The base implementation of `_.isNative` without bad shim checks.
*
* @private
* @param {*} value The value to check.
* @returns {boolean} Returns `true` if `value` is a native function,
* else `false`.
*/
function baseIsNative(value) {
if (!isObject(value) || isMasked(value)) {
return false;
}
var pattern = (isFunction(value) || isHostObject(value)) ? reIsNative : reIsHostCtor;
return pattern.test(toSource(value));
}
/**
* The base implementation of `_.keys` which doesn't treat sparse arrays as dense.
*
* @private
* @param {Object} object The object to query.
* @returns {Array} Returns the array of property names.
*/
function baseKeys(object) {
if (!isPrototype(object)) {
return nativeKeys(object);
}
var result = [];
for (var key in Object(object)) {
if (hasOwnProperty.call(object, key) && key != 'constructor') {
result.push(key);
}
}
return result;
}
/**
* Creates a clone of `buffer`.
*
* @private
* @param {Buffer} buffer The buffer to clone.
* @param {boolean} [isDeep] Specify a deep clone.
* @returns {Buffer} Returns the cloned buffer.
*/
function cloneBuffer(buffer, isDeep) {
if (isDeep) {
return buffer.slice();
}
var result = new buffer.constructor(buffer.length);
buffer.copy(result);
return result;
}
/**
* Creates a clone of `arrayBuffer`.
*
* @private
* @param {ArrayBuffer} arrayBuffer The array buffer to clone.
* @returns {ArrayBuffer} Returns the cloned array buffer.
*/
function cloneArrayBuffer(arrayBuffer) {
var result = new arrayBuffer.constructor(arrayBuffer.byteLength);
new Uint8Array(result).set(new Uint8Array(arrayBuffer));
return result;
}
/**
* Creates a clone of `dataView`.
*
* @private
* @param {Object} dataView The data view to clone.
* @param {boolean} [isDeep] Specify a deep clone.
* @returns {Object} Returns the cloned data view.
*/
function cloneDataView(dataView, isDeep) {
var buffer = isDeep ? cloneArrayBuffer(dataView.buffer) : dataView.buffer;
return new dataView.constructor(buffer, dataView.byteOffset, dataView.byteLength);
}
/**
* Creates a clone of `map`.
*
* @private
* @param {Object} map The map to clone.
* @param {Function} cloneFunc The function to clone values.
* @param {boolean} [isDeep] Specify a deep clone.
* @returns {Object} Returns the cloned map.
*/
function cloneMap(map, isDeep, cloneFunc) {
var array = isDeep ? cloneFunc(mapToArray(map), true) : mapToArray(map);
return arrayReduce(array, addMapEntry, new map.constructor);
}
/**
* Creates a clone of `regexp`.
*
* @private
* @param {Object} regexp The regexp to clone.
* @returns {Object} Returns the cloned regexp.
*/
function cloneRegExp(regexp) {
var result = new regexp.constructor(regexp.source, reFlags.exec(regexp));
result.lastIndex = regexp.lastIndex;
return result;
}
/**
* Creates a clone of `set`.
*
* @private
* @param {Object} set The set to clone.
* @param {Function} cloneFunc The function to clone values.
* @param {boolean} [isDeep] Specify a deep clone.
* @returns {Object} Returns the cloned set.
*/
function cloneSet(set, isDeep, cloneFunc) {
var array = isDeep ? cloneFunc(setToArray(set), true) : setToArray(set);
return arrayReduce(array, addSetEntry, new set.constructor);
}
/**
* Creates a clone of the `symbol` object.
*
* @private
* @param {Object} symbol The symbol object to clone.
* @returns {Object} Returns the cloned symbol object.
*/
function cloneSymbol(symbol) {
return symbolValueOf ? Object(symbolValueOf.call(symbol)) : {};
}
/**
* Creates a clone of `typedArray`.
*
* @private
* @param {Object} typedArray The typed array to clone.
* @param {boolean} [isDeep] Specify a deep clone.
* @returns {Object} Returns the cloned typed array.
*/
function cloneTypedArray(typedArray, isDeep) {
var buffer = isDeep ? cloneArrayBuffer(typedArray.buffer) : typedArray.buffer;
return new typedArray.constructor(buffer, typedArray.byteOffset, typedArray.length);
}
/**
* Copies properties of `source` to `object`.
*
* @private
* @param {Object} source The object to copy properties from.
* @param {Array} props The property identifiers to copy.
* @param {Object} [object={}] The object to copy properties to.
* @param {Function} [customizer] The function to customize copied values.
* @returns {Object} Returns `object`.
*/
function copyObject(source, props, object, customizer) {
object || (object = {});
var index = -1,
length = props.length;
while (++index < length) {
var key = props[index];
var newValue = customizer
? customizer(object[key], source[key], key, object, source)
: undefined;
assignValue(object, key, newValue === undefined ? source[key] : newValue);
}
return object;
}
/**
* Copies own symbol properties of `source` to `object`.
*
* @private
* @param {Object} source The object to copy symbols from.
* @param {Object} [object={}] The object to copy symbols to.
* @returns {Object} Returns `object`.
*/
function copySymbols(source, object) {
return copyObject(source, getSymbols(source), object);
}
/**
* Creates an array of own enumerable property names and symbols of `object`.
*
* @private
* @param {Object} object The object to query.
* @returns {Array} Returns the array of property names and symbols.
*/
function getAllKeys(object) {
return baseGetAllKeys(object, keys, getSymbols);
}
/**
* Gets the data for `map`.
*
* @private
* @param {Object} map The map to query.
* @param {string} key The reference key.
* @returns {*} Returns the map data.
*/
function getMapData(map, key) {
var data = map.__data__;
return isKeyable(key)
? data[typeof key == 'string' ? 'string' : 'hash']
: data.map;
}
/**
* Gets the native function at `key` of `object`.
*
* @private
* @param {Object} object The object to query.
* @param {string} key The key of the method to get.
* @returns {*} Returns the function if it's native, else `undefined`.
*/
function getNative(object, key) {
var value = getValue(object, key);
return baseIsNative(value) ? value : undefined;
}
/**
* Creates an array of the own enumerable symbol properties of `object`.
*
* @private
* @param {Object} object The object to query.
* @returns {Array} Returns the array of symbols.
*/
var getSymbols = nativeGetSymbols ? overArg(nativeGetSymbols, Object) : function () {
return []
};
/**
* Gets the `toStringTag` of `value`.
*
* @private
* @param {*} value The value to query.
* @returns {string} Returns the `toStringTag`.
*/
var getTag = function (value) {
return objectToString.call(value);
};
// Fallback for data views, maps, sets, and weak maps in IE 11,
// for data views in Edge < 14, and promises in Node.js.
if ((DataView && getTag(new DataView(new ArrayBuffer(1))) != dataViewTag) ||
(Map && getTag(new Map) != mapTag) ||
(Promise && getTag(Promise.resolve()) != promiseTag) ||
(Set && getTag(new Set) != setTag) ||
(WeakMap && getTag(new WeakMap) != weakMapTag)) {
getTag = function(value) {
var result = objectToString.call(value),
Ctor = result == objectTag ? value.constructor : undefined,
ctorString = Ctor ? toSource(Ctor) : undefined;
if (ctorString) {
switch (ctorString) {
case dataViewCtorString: return dataViewTag;
case mapCtorString: return mapTag;
case promiseCtorString: return promiseTag;
case setCtorString: return setTag;
case weakMapCtorString: return weakMapTag;
}
}
return result;
};
}
/**
* Initializes an object clone.
*
* @private
* @param {Object} object The object to clone.
* @returns {Object} Returns the initialized clone.
*/
function initCloneObject(object) {
return (typeof object.constructor == 'function' && !isPrototype(object))
? baseCreate(getPrototype(object))
: {};
}
/**
* Initializes an object clone based on its `toStringTag`.
*
* **Note:** This function only supports cloning values with tags of
* `Boolean`, `Date`, `Error`, `Number`, `RegExp`, or `String`.
*
* @private
* @param {Object} object The object to clone.
* @param {string} tag The `toStringTag` of the object to clone.
* @param {Function} cloneFunc The function to clone values.
* @param {boolean} [isDeep] Specify a deep clone.
* @returns {Object} Returns the initialized clone.
*/
function initCloneByTag(object, tag, cloneFunc, isDeep) {
var Ctor = object.constructor;
switch (tag) {
case arrayBufferTag:
return cloneArrayBuffer(object);
case boolTag:
case dateTag:
return new Ctor(+object);
case dataViewTag:
return cloneDataView(object, isDeep);
case float32Tag: case float64Tag:
case int8Tag: case int16Tag: case int32Tag:
case uint8Tag: case uint8ClampedTag: case uint16Tag: case uint32Tag:
return cloneTypedArray(object, isDeep);
case mapTag:
return cloneMap(object, isDeep, cloneFunc);
case numberTag:
case stringTag:
return new Ctor(object);
case regexpTag:
return cloneRegExp(object);
case setTag:
return cloneSet(object, isDeep, cloneFunc);
case symbolTag:
return cloneSymbol(object);
}
}
/**
* Checks if `value` is a valid array-like index.
*
* @private
* @param {*} value The value to check.
* @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
* @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
*/
function isIndex(value, length) {
length = length == null ? MAX_SAFE_INTEGER : length;
return !!length &&
(typeof value == 'number' || reIsUint.test(value)) &&
(value > -1 && value % 1 == 0 && value < length);
}
/**
* Checks if `value` is suitable for use as unique object key.
*
* @private
* @param {*} value The value to check.
* @returns {boolean} Returns `true` if `value` is suitable, else `false`.
*/
function isKeyable(value) {
var type = typeof value;
return (type == 'string' || type == 'number' || type == 'symbol' || type == 'boolean')
? (value !== '__proto__')
: (value === null);
}
/**
* Checks if `func` has its source masked.
*
* @private
* @param {Function} func The function to check.
* @returns {boolean} Returns `true` if `func` is masked, else `false`.
*/
function isMasked(func) {
return !!maskSrcKey && (maskSrcKey in func);
}
/**
* Checks if `value` is likely a prototype object.
*
* @private
* @param {*} value The value to check.
* @returns {boolean} Returns `true` if `value` is a prototype, else `false`.
*/
function isPrototype(value) {
var Ctor = value && value.constructor,
proto = (typeof Ctor == 'function' && Ctor.prototype) || objectProto;
return value === proto;
}
/**
* Converts `func` to its source code.
*
* @private
* @param {Function} func The function to process.
* @returns {string} Returns the source code.
*/
function toSource(func) {
if (func != null) {
try {
return funcToString.call(func);
} catch (e) {}
try {
return (func + '');
} catch (e) {}
}
return '';
}
/**
* Performs a
* [`SameValueZero`](http://ecma-international.org/ecma-262/7.0/#sec-samevaluezero)
* comparison between two values to determine if they are equivalent.
*
* @static
* @memberOf _
* @since 4.0.0
* @category Lang
* @param {*} value The value to compare.
* @param {*} other The other value to compare.
* @returns {boolean} Returns `true` if the values are equivalent, else `false`.
* @example
*
* var object = { 'a': 1 };
* var other = { 'a': 1 };
*
* _.eq(object, object);
* // => true
*
* _.eq(object, other);
* // => false
*
* _.eq('a', 'a');
* // => true
*
* _.eq('a', Object('a'));
* // => false
*
* _.eq(NaN, NaN);
* // => true
*/
function eq(value, other) {
return value === other || (value !== value && other !== other);
}
/**
* Checks if `value` is likely an `arguments` object.
*
* @static
* @memberOf _
* @since 0.1.0
* @category Lang
* @param {*} value The value to check.
* @returns {boolean} Returns `true` if `value` is an `arguments` object,
* else `false`.
* @example
*
* _.isArguments(function() { return arguments; }());
* // => true
*
* _.isArguments([1, 2, 3]);
* // => false
*/
function isArguments(value) {
// Safari 8.1 makes `arguments.callee` enumerable in strict mode.
return isArrayLikeObject(value) && hasOwnProperty.call(value, 'callee') &&
(!propertyIsEnumerable.call(value, 'callee') || objectToString.call(value) == argsTag);
}
/**
* Checks if `value` is array-like. A value is considered array-like if it's
* not a function and has a `value.length` that's an integer greater than or
* equal to `0` and less than or equal to `Number.MAX_SAFE_INTEGER`.
*
* @static
* @memberOf _
* @since 4.0.0
* @category Lang
* @param {*} value The value to check.
* @returns {boolean} Returns `true` if `value` is array-like, else `false`.
* @example
*
* _.isArrayLike([1, 2, 3]);
* // => true
*
* _.isArrayLike(document.body.children);
* // => true
*
* _.isArrayLike('abc');
* // => true
*
* _.isArrayLike(_.noop);
* // => false
*/
function isArrayLike(value) {
return value != null && isLength(value.length) && !isFunction(value);
}
function isArrayLikeObject(value) {
let res = !!value && typeof value == 'object'
return res && isArrayLike(value);
}
/**
* Checks if `value` is classified as a `Function` object.
*
* @static
* @memberOf _
* @since 0.1.0
* @category Lang
* @param {*} value The value to check.
* @returns {boolean} Returns `true` if `value` is a function, else `false`.
* @example
*
* _.isFunction(_);
* // => true
*
* _.isFunction(/abc/);
* // => false
*/
function isFunction(value) {
// The use of `Object#toString` avoids issues with the `typeof` operator
// in Safari 8-9 which returns 'object' for typed array and other constructors.
var tag = isObject(value) ? objectToString.call(value) : '';
return tag == funcTag || tag == genTag;
}
function isLength(value) {
return typeof value == 'number' &&
value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
}
function isObject(value) {
var type = typeof value;
return !!value && (type == 'object' || type == 'function');
}
/**
* Creates an array of the own enumerable property names of `object`.
*
* **Note:** Non-object values are coerced to objects. See the
* [ES spec](http://ecma-international.org/ecma-262/7.0/#sec-object.keys)
* for more details.
*
* @static
* @since 0.1.0
* @memberOf _
* @category Object
* @param {Object} object The object to query.
* @returns {Array} Returns the array of property names.
* @example
*
* function Foo() {
* this.a = 1;
* this.b = 2;
* }
*
* Foo.prototype.c = 3;
*
* _.keys(new Foo);
* // => ['a', 'b'] (iteration order is not guaranteed)
*
* _.keys('hi');
* // => ['0', '1']
*/
function keys(object) {
return isArrayLike(object) ? arrayLikeKeys(object) : baseKeys(object);
}代码有点长，容我再整理整理。
