react报错index.jsx:8 Uncaught TypeError: Cannot read properties of undefined (reading ‘map‘)

在react时使用map遍历数组报错index.jsx:8 Uncaught TypeError: Cannot read properties of undefined (reading ‘map’)

这是因为第一次数组里面是空数组，没有值，所以需要对其进行遍历
错误代码：

<ul className="todo-main">
   {
      todos.map((todoObj)=>{
        return <Items key={todoObj.id} {...todoObj}/>
      })
    }
</ul>

正确代码：

 <ul className="todo-main">
    {
       todos && todos.map((todoObj)=>{
         return <Items key={todoObj.id} {...todoObj}/>
       })
     }
</ul>