如何将 JavaScript 中的数据缓冲区转换为文件？

Question

我正在从客户端的节点/express 端点接收数据缓冲区，并且我想将缓冲区转换为文件。

该文件可以是 pdf、文本文档或图像。端点告诉我的唯一信息是它正在发送一个八位字节流。

我该怎么做呢？

这是我迄今为止在客户端的代码

const xhr = new XMLHttpRequest();
xhr.open("POST", "MY_URL", true);
xhr.responseType = "arraybuffer";

// I need to send some data for the request
xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");

// send request
xhr.send(`identifier=${myIdentifier}`);

xhr.onload = function (xEvent)
{
    const arrayBuffer = xhr.response;
    if (arrayBuffer)
    {
        const byteArray = new Uint8Array(arrayBuffer);

        const url = window.URL.createObjectURL(new Blob([byteArray]));

        const link = document.createElement("a");
        link.href = url;
        link.setAttribute("download", "file.pdf"); //or any other extension
        document.body.appendChild(link);
        link.click();
    }
};

Answer 1

将arraybuffer转换为base64，然后转换为url，生成fileUrl用于查看

arrayBufferToBase64(Arraybuffer, Filetype, fileName) {
        let binary = '';
        const bytes = new Uint8Array(Arraybuffer);
        const len = bytes.byteLength;
        for (let i = 0; i < len; i++) {
          binary += String.fromCharCode(bytes[i]);
        }
        const file = window.btoa(binary);
        const mimType = Filetype === 'pdf' ? 'application/pdf' : Filetype === 'xlsx' ? 'application/xlsx' :
          Filetype === 'pptx' ? 'application/pptx' : Filetype === 'csv' ? 'application/csv' : Filetype === 'docx' ? 'application/docx' :
            Filetype === 'jpg' ? 'application/jpg' : Filetype === 'png' ? 'application/png' : '';
        const url = `data:${mimType};base64,` + file;
    
        // url for the file
        this.fileUrl = this.sanitizer.bypassSecurityTrustResourceUrl(url);
    
        // download the file
          const a = document.createElement('a');
          a.href = url;
          a.download = fileName;
          document.body.appendChild(a);
          a.click();
          document.body.removeChild(a);
          window.URL.revokeObjectURL(url);
      }