javascript - 后端返回JSON编码后的数据，在前端axios接受之后，就是转为了JavaScript对应的对象是吗？

Question

使用Express作为后端程序，
通过JSON编码后返回数据：

const data = JSON.stringify(originData)
res.send(`${data}`);

前端在接受到之后：

  useEffect(() => {
    
    console.log(111)
    axios.get('http://localhost:3000/blocks/1').then((res) => {
      console.log(JSON.stringify(res.data.results))  // 这里有数据
      
      const blocksRes = res.data.results

      console.log(typeof blocksRes)  // 打印的是：object
      setBlocks(res.data.results)
    })

  }, [])

这里有一个疑问，

1、后端返回JSON编码后的数据，在前端axios接受之后，就是转为了JavaScript对应的对象是吗？
2、这里打印的是一个数组样式的数据：

 console.log(JSON.stringify(res.data.results))   

结果：

[{"object":"block","id":"17ddeaa8-cb4b-803e-9807-e9197656cee6","parent":{"type":"page_id","page_id":"17ddeaa8-cb4b-8092-9a2c-c1617a013cdd"},"created_time":"2025-01-16T10:35:00.000Z","last_edited_time":"2025-02-07T07:06:00.000Z","createdUser":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"last_edited_by":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"has_children":false,"archived":false,"Rrash":false,"type":"paragraph","paragraph":{"rich_text":[{"type":"text","text":{"content":"11","link":null},"annotations":{"bold":false,"italic":false,"strikethrough":false,"underline":false,"code":false,"color":"default"},"plain_text":"11","href":null}],"color":"default"}},{"object":"block","id":"193deaa8-cb4b-807c-907d-c36955a9904f","parent":{"type":"page_id","page_id":"17ddeaa8-cb4b-8092-9a2c-c1617a013cdd"},"created_time":"2025-02-07T07:06:00.000Z","last_edited_time":"2025-02-07T08:54:00.000Z","createdUser":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"last_edited_by":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"has_children":false,"archived":false,"Rrash":false,"type":"paragraph","paragraph":{"rich_text":[{"type":"text","text":{"content":"22","link":null},"annotations":{"bold":false,"italic":false,"strikethrough":false,"underline":false,"code":false,"color":"default"},"plain_text":"22","href":null}],"color":"default"}},{"object":"block","id":"193deaa8-cb4b-8019-9543-f2a38aa45c23","parent":{"type":"page_id","page_id":"17ddeaa8-cb4b-8092-9a2c-c1617a013cdd"},"created_time":"2025-02-07T08:54:00.000Z","last_edited_time":"2025-02-07T08:54:00.000Z","createdUser":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"last_edited_by":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"has_children":false,"archived":false,"Rrash":false,"type":"paragraph","paragraph":{"rich_text":[],"color":"default"}},{"object":"block","id":"193deaa8-cb4b-80ee-833b-c63b0abe9395","parent":{"type":"page_id","page_id":"17ddeaa8-cb4b-8092-9a2c-c1617a013cdd"},"created_time":"2025-02-07T08:54:00.000Z","last_edited_time":"2025-02-07T08:55:00.000Z","createdUser":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"last_edited_by":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"has_children":false,"archived":false,"Rrash":false,"type":"code","code":{"caption":[],"rich_text":[{"type":"text","text":{"content":"{\n  aaa: 111,\n  bbb: 222,\n}","link":null},"annotations":{"bold":false,"italic":false,"strikethrough":false,"underline":false,"code":false,"color":"default"},"plain_text":"{\n  aaa: 111,\n  bbb: 222,\n}","href":null}],"language":"json"}},{"object":"block","id":"193deaa8-cb4b-8040-8014-ccf112c8b971","parent":{"type":"page_id","page_id":"17ddeaa8-cb4b-8092-9a2c-c1617a013cdd"},"created_time":"2025-02-07T08:55:00.000Z","last_edited_time":"2025-02-07T08:55:00.000Z","createdUser":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"last_edited_by":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"has_children":false,"archived":false,"Rrash":false,"type":"paragraph","paragraph":{"rich_text":[],"color":"default"}},{"object":"block","id":"193deaa8-cb4b-80d2-91d6-d950d3d73dc2","parent":{"type":"page_id","page_id":"17ddeaa8-cb4b-8092-9a2c-c1617a013cdd"},"created_time":"2025-02-07T08:55:00.000Z","last_edited_time":"2025-02-07T08:55:00.000Z","createdUser":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"last_edited_by":{"object":"user","id":"4dbd-acb7-6d3fd574055822"},"has_children":false,"archived":false,"Rrash":false,"type":"paragraph","paragraph":{"rich_text":[],"color":"default"}}]

这里看出是一个数组，为何：这里打印是object呢？

console.log(typeof blocksRes)  // 打印的是：object

Answer 1

Axios 会根据响应的 Content-Type 头部，自动解析 JSON 数据并将其转换为 JavaScript 对象.
如果你不想让 Axios 自动解析 JSON，可以通过设置 responseType 来更改行为，例如 responseType: 'text'

Answer 2

对于问题二，JavaScript的typeof 数组返回的就是object，可以用Array.isArray或者instanceof判断数组。

typeof []
// 'object'
[] instanceof Array
// true
Array.isArray([])
// true