1、创建对象

  1. ![7a.png](https://cdn.nlark.com/yuque/0/2022/png/28344462/1652105320972-694bd96d-32f5-44ec-bb4c-fb772e3bb86a.png#clientId=u1046486a-2f7d-4&crop=0&crop=0&crop=1&crop=1&from=ui&id=u69460200&margin=%5Bobject%20Object%5D&name=7a.png&originHeight=304&originWidth=970&originalType=binary&ratio=1&rotation=0&showTitle=false&size=45160&status=done&style=none&taskId=u75e7c0b9-abe8-4706-b7de-f8598c6ca65&title=)

2、常用方法

  1. ![56.png](https://cdn.nlark.com/yuque/0/2022/png/28344462/1652105358752-8637a7b9-fc62-453b-9072-887952ca603e.png#clientId=u1046486a-2f7d-4&crop=0&crop=0&crop=1&crop=1&from=ui&id=ua9afdf33&margin=%5Bobject%20Object%5D&name=56.png&originHeight=398&originWidth=962&originalType=binary&ratio=1&rotation=0&showTitle=false&size=44542&status=done&style=none&taskId=u9eaa73be-0ab2-4729-adb6-d5bc78ebb78&title=)