缓冲区的字节大小(JavaScript/节点) [英] byte size of buffer (Javascript / Node)

问题描述

如何在javascript中获取缓冲图像的大小(以字节为单位)?我不允许在客户端信任文件大小，因此需要在后端进行验证，以作为上传验证的一部分.我的设置如下:

How do I get the size (in bytes) of a bufferd image in javascript? I am not allowed to trust the file size in the client side, and need to verify in the backend as part of upload validation. My setup is as follows:

1-我将文件上传到客户端，然后从React组件发送到Node:

1- I upload a file in the client and send it to Node from a React component:

      fileUpload() {
          const url = '/.../...'
          const formData = new FormData()
          formData.append('file', this.state.file)
          formData.append('actualSize', this.state.file.size) //not allowed to use this.
          const config = { headers: { 'content-type': 'multipart/form-data' } }
          axios.post(url, formData, config)
      }

2-使用一些中间件，我将Node中的数据作为对象接收:

2- Using some middleware, I receive the data in Node as an object:

  { 
      file: { 
            name: 'test',
            data: <Buffer 12 50 4e ... >,
            encoding: '7bit',
            mimetype: 'image/png',
      } 
  }

如何测量缓冲区的字节大小?预先感谢！

How can I measure the byte size of the buffer? Thanks in advance!

推荐答案

类似于 file.data.byteLength 或 file.data.toString().length 的东西会返回以 byte 为单位的大小，除以1024得到以 kb

something like file.data.byteLength or file.data.toString().length will return the size in byte, divide with 1024 to get the size in kb

https://nodejs.org/api/buffer.html#buffer_class_method_buffer_bytelength_string_encoding

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