refactor(deepClone)

articles/write/deep_clone.md

@@ -5,53 +5,138 @@ author: lvzl
 
 ## 深拷贝
 ```js
-function clone(dest, source, map = new WeakMap()) {
-  if (!isObjectOrArray(dest) || !isObjectOrArray(source)) {
-    return dest
-  }
-  if (map.get(source)) {
-    return source
-  }
-  map.set(source, true)
-  for (const key in source) {
-    if(isObject(source[key])) {
-      dest[key] = clone({}, source[key], map)
-    } else if(Array.isArray(source[key])) {
-      dest[key] = clone([], source[key], map)
-    } else {
-      dest[key] = source[key]
-    }
+/**
+ * clone 要区分很多种类型
+ * Undefined、Null、Boolean、Number、String、Array、Object、Function、Map、Set、WeakMap、WeakSet、Symbol、BigInt、Date、Regexp、Arguments
+ * 可枚举类型：Object Array Map Set Arguments
+ * 可直接赋值：'undefined', 'string','number','boolean','symbol','bigint'
+ * 要特殊处理的类型 function Error
+ * 这些用法需要特殊处理：new Number(2)、new String('')、new RegExp(//)、new Boolean(false)、new Date()、new Error()
+ */
+
+// while 循环更快
+const foreach = (keys, cb) => {
+  let i = 0
+  while(i < keys.length) {
+    cb(keys[i])
+    i++
   }
-  return dest
 }
+// 可继续遍历
+const mapTag = '[object Map]'
+const setTag = '[object Set]'
+const arrayTag = '[object Array]'
+const objectTag = '[object Object]'
+const arguTag = '[object Arguments]'
+
+const canFor = [ mapTag, setTag, arrayTag, objectTag, arguTag ]
 
-function isObjectOrArray(obj) {
-  const type = Object.prototype.toString.call(obj)
-  return type === '[object Object]' || type === '[object Array]'
+// 特殊
+const funcTag = '[object Function]'
+const regExpTag = '[object RegExp]'
+const errorTag = Error
+
+const getType = (val) => {
+  return Object.prototype.toString.call(val)
 }
 
-function isObject(obj) {
-  return Object.prototype.toString.call(obj) === '[object Object]'
+const isNormalType = val => {
+  if (val === null) {
+    return true
+  }
+  const typ = typeof val
+  return ['undefined', 'string','number','boolean','symbol','bigint'].includes(typ)
+}
+/**
+ * 复制一个函数
+ * @param {} fn 
+ */
+const cloneFunction = (fn) => {
+  const fnStr = fn.toLocaleString()
+  if (/((function\s+)\w*\s*\()|^\(/.test(fnStr)) {
+    return eval('(() => (' + fnStr + '))()')
+  }
+  return eval('(() => (function ' + fnStr + '))()')
 }
 
-function isArray(obj) {
-  return Array.isArray(obj)
+/**
+ * 比如 new Number(2)、new String('')、new RegExp()、new Boolean(false)、new Date()、new Error()
+ * @param {*} fn 
+ */
+const cloneObjectCanNotFor = (val) => {
+  const ctor = val.constructor
+  let value = val.valueOf()
+  if (ctor === errorTag) { // 特殊一点，获取到的信息替换一下 Error: 
+    value = value.message
+  }
+  return new ctor(value)
 }
 
-// test
-const source = {
-  a: 1,
-  b: 2,
-  c: null,
-  d: undefined,
-  e: '',
-  f: [1,2,3],
-  g: {
-    h: 20,
-    i: {j: '123', k: [{l: 888}]}
+function deepClone(val, map = new WeakMap()) {
+  //  非对象类型的： string、number、boolean、symbol、bigint、null false undefined，这些可直接赋值
+  if (isNormalType(val)) {
+    return val
   }
+  // 接下来都是 typeof 为 object ，先获取具体的类型
+  const typ = getType(val)
+
+  if (map.has(val)) {
+    return map.get(val)
+  }
+
+  // function
+  if(typ === funcTag) {
+    return cloneFunction(val)
+  }
+
+  let res
+
+  // 可枚举的
+  if(canFor.includes(typ)) {
+    if(typ === objectTag || typ === arrayTag || typ === arguTag) {
+      res = Array.isArray(val) ? [] : {}
+      const keys = Object.keys(val)
+      foreach(keys, key => {
+        res[key] = deepClone(val[key], map)
+      })
+    } else if (typ === setTag) {
+      res = new Set()
+      val.forEach(s => {
+        res.add(deepClone(s))
+      })
+    } else if (typ === mapTag) {
+      res = new Map()
+      val.forEach(mapkey => {
+        res.set(mapkey, deepClone(val.get(mapkey)))
+      })
+    }
+    map.set(val, res)
+  } else {
+    return cloneObjectCanNotFor(val)
+  }
+  return res
+}
+
+// Undefined、Null、Boolean、Number、String、Array、Object、Function、Map、Set、WeakMap、WeakSet、Symbol、BigInt、Date、Regexp、Arguments
+const obj = {
+  a: null,
+  b: undefined,
+  c: [1,2,3],
+  d: false,
+  e: true,
+  f: 33444,
+  g: '46576',
+  i: {aa: '', bb: 3},
+  j() {},
+  h: new Map().set({}, 2),
+  k: new Set().add(344, 'ee'),
+  l: Symbol('d'),
+  m: BigInt(12346575),
+  n: new Date('2023-01-01'),
+  o: new Error('haha'),
+  p: () => { console.log('jiantouhanshu') },
+  r: new RegExp('function')
 }
-source.s = source
 
-const aaa = clone({}, source)
+const f = deepClone(obj)
 ```