Symbol 函数前不能使用 new 命令，否则会报错。这是因为生成的 Symbol 是一个原始类型的值，不是对象。
+
Symbol 值不能与其他类型的值进行运算，会报错。
+
+
+
+
\ No newline at end of file
diff --git a/for0f.js b/for0f.js
new file mode 100644
index 0000000..1ddd701
--- /dev/null
+++ b/for0f.js
@@ -0,0 +1,13 @@
+function forOf(obj, cb) {
+ let iterable, result
+ if (typeof obj[Symbol.iterator] !== 'function') {
+ throw new TypeError(obj + ' is not iterable')
+ }
+ if (typeof cb !== 'function') throw new TypeError('cb must bu calllable')
+ iterable = obj[Symbol.iterator]()
+ result = iterable.next()
+ while (!result.done) {
+ cb(result.value)
+ result = iterable.next()
+ }
+}
\ No newline at end of file
diff --git a/index.html b/index.html
index 2dde5c0..2079a48 100644
--- a/index.html
+++ b/index.html
@@ -8,6 +8,7 @@
+
diff --git "a/set\344\270\216map/map.js" "b/set\344\270\216map/map.js"
index 3513e78..edc0eb2 100644
--- "a/set\344\270\216map/map.js"
+++ "b/set\344\270\216map/map.js"
@@ -4,4 +4,27 @@ const o = { name: 'object' }
m.set(o, 1)
m.get(o)
-console.log(m.has(o))
\ No newline at end of file
+console.log(m.has(o))
+
+
+// WeakMap 只接受对象作为键名
+// WeakMap 的键名所引用的对象是弱引用 弱引用就是能够被垃圾回收的引用
+
+
+const privateData = new WeakMap();
+
+class Person {
+ constructor(name, age) {
+ privateData.set(this, { name: name, age: age });
+ }
+
+ getName() {
+ return privateData.get(this).name;
+ }
+
+ getAge() {
+ return privateData.get(this).age;
+ }
+}
+
+export default Person;
\ No newline at end of file
diff --git a/symbol.js b/symbol.js
new file mode 100644
index 0000000..dd76b62
--- /dev/null
+++ b/symbol.js
@@ -0,0 +1,68 @@
+var generateName = (function () {
+ var endfix = 0
+ return function (desc) {
+ endfix++
+ return `@@${desc}_${endfix}`
+ }
+})()
+
+var SymbolPolyfill = function Symbol(desc) {
+ if (this instanceof SymbolPolyfill) throw new TypeError('Symbom is not a function')
+ var descString = desc === undefined ? undefined : String(desc)
+ var symbol = Object.create({
+ toString: function () {
+ return this.__Name__
+ },
+ valueOf: function () {
+ throw new Error('Cannot convert a Symbol value')
+ }
+ })
+ Object.defineProperties(symbol, {
+ '__Description__': {
+ value: descString,
+ writable: false,
+ enumerable: false,
+ configurable: false
+ },
+ '__Name__': {
+ value: generateName(descString),
+ writable: false,
+ enumerable: false,
+ configurable: false
+ }
+ })
+ return symbol
+}
+
+var forMap = {}
+Object.defineProperties(SymbolPolyfill, {
+ 'for': {
+ value: function (desc) {
+ var descString = desc === undefined ? undefined : String(desc)
+ return forMap[descString] ? forMap[descString] : forMap[descString] = SymbolPolyfill(descString)
+ },
+ writable: true,
+ enumerable: false,
+ configurable: true
+ },
+ 'keyFor': {
+ value: function (symbol) {
+ for (let key in forMap) {
+ if(forMap[key] === symbol) return key
+ }
+ },
+ writable: true,
+ enumerable: false,
+ configurable: true
+ }
+})
+
+var a = SymbolPolyfill('a')
+var b = SymbolPolyfill('a')
+console.log(a === b)
+console.log(a.toString())
+var obj = {}
+obj[a] = '1111'
+obj[b] = '222'
+console.log(obj)
+// console.log(a + 1)
\ No newline at end of file
diff --git "a/\345\256\236\347\216\260\344\270\200\344\270\252\347\256\200\345\215\225\347\232\204promise.js" "b/\345\256\236\347\216\260\344\270\200\344\270\252\347\256\200\345\215\225\347\232\204promise.js"
index ae21c59..0966782 100644
--- "a/\345\256\236\347\216\260\344\270\200\344\270\252\347\256\200\345\215\225\347\232\204promise.js"
+++ "b/\345\256\236\347\216\260\344\270\200\344\270\252\347\256\200\345\215\225\347\232\204promise.js"
@@ -174,3 +174,33 @@
window.Promise = Promise
}(window)
+
+function red() {
+ console.log('red')
+}
+function green() {
+ console.log('green')
+}
+function yellow() {
+ console.log('yellow')
+}
+
+function light(cb, timer) {
+ return new Promise((resolve, reject) => {
+ setTimeout(() => {
+ cb()
+ resolve()
+ }, timer);
+ })
+}
+
+function change() {
+ light(red, 3000).
+ then(() => {
+ return light(green, 2000)
+ }).then(() => {
+ return light(yellow, 2000)
+ }).then(() => {
+ change()
+ })
+}
\ No newline at end of file