Facing Error when Converting Base64 to PDF file in ReactJS/Javascript

Question

i am struggling to display the PDF as attachment in ReactJS. i have managed to bring the base64 to the front end but after i try to create the blob object it doesn't work and although it goes to the Acrobat reader but shows the error. any suggestions please as how can i convert base64 to pdf correctly.

I have also uploaded the base64 code that i am getting when console logging at pastebin, https://pastebin.com/W4zEXyPy

Note: As when i try to repair at https://base64.guru/ it shows invalid strings and character(data:application/pdf;), i have tried to use content.slice(29); so it will start from JVB...(rather from data:application/pdf;base64,JVBERi0xL........) but getting the same error. Link to pic of Repair Base64 atbase64guru

Error: not decoded properly

• NodeJS baackend code responding to API call

       let token = req.cookies.access_token;
           if (token) {
             let Invoice_No_Actual = req.body.invoice_Name;
             res.set("Content-disposition", "attachment; filename=" + `${__dirname}\\` + `${Invoice_No_Actual}` + `.pdf`);
             res.contentType("application/pdf");
             res.send(`data:application/pdf;base64,${new Buffer.from(data).toString("base64")}`);
           }
         });
  

• Frontend code API call

   const headers = new Headers();
          headers.append("content-type", "application/json");
          headers.append("responseType", "application/pdf");
  
          const options = {
            method: "POST",
            headers,
            credentials: "include",
            body: JSON.stringify(invoice_Object),
            // body: "My HTML String",
          };
  
          const newRequest = new Request("http://localhost:5000/api/invoice-only", options);
  
          (async () => {
            const invoice_Call = await fetch(newRequest)
              .then((res) => {
                return text1 = res.text();
              })
              .then((data) => {
               generateFile(data, invoice_Name);
              });
          })();
        };
  

• generateFile() function call Front End- after receiving the response

    let generateFile = (content, fileName) => {
    
        console.log("content", content); // here at console if i copy the code and use online tool(https://base64.guru/converter/decode/pdf) it shows the correct pdf

        let content1= content.slice(29);// content1 is correct base64 as if i use it online tool it correctly generate the PDF document
        const blob = new Blob([content1], { type: "application/pdf" });
        console.log(blob);
        const link = document.createElement("a");
        link.href = window.URL.createObjectURL(blob);
        link.download = fileName;
        link.click();
      };

• Error when opening Link to PDF file Error pic

Answer 1

A simple console.log(content.slice(29)) could reveal your mistake. The problem is that the content1 variable contains a string that begins with "VBE…" while it must begin with "JVBE…". So, your mistake is that the slice() function discards too many characters.