Update map.md

docs/uts/buildin-object-api/map.md

@@ -90,3 +90,33 @@ console.log(map1.get('bar'));
 console.log(map1.get('baz'));
 // expected output: null
 ```
+
+### 常见操作
+
+- 创建map
+```ts
+let map = new Map<string,any>()
+map.put("name","zhangsan")
+map.put("age",12)
+//Map(2) {"name":"zhangsan","age":12} 
+console.log(map)
+```
+- 通过key访问map元素
+```ts
+let map = new Map<string,any>()
+map.put("name","zhangsan")
+map.put("age",12)
+let nameVal = map['name']
+//zhangsan
+console.log(nameVal)
+```
+- 遍历map
+```ts
+let map = new Map<string,any>()
+map.put("name","zhangsan")
+map.put("age",12)
+map.forEach(function(key:string,value:any){
+    console.log(key)
+    console.log(value)
+})
+```