Return a File object from a local filepath in NodeJS

Question

I am trying to write a function that returns me a Blob or File object, blob_object, while taking in the local filepath of an object, tmpFilePath, and I have to use NodeJS to do it as the function is used as part of a Firebase cloud function. I have tried many methods, but none of them work. They mainly revolve around this.

Attempt 1: Using streamToBlob. Inspired from reddit

const streamToBlob = require('stream-to-blob');
const fs = require('fs-extra');


const input_read_stream = fs.createReadStream(tmpFilePath);
const blob_object = await streamToBlob(input_read_stream);

Error: ReferenceError: Blob is not defined

Attempt 2: using blob. Inspired from stackoverflow

const Blob = require('blob');
const fs = require('fs-extra');

const file_buffer = fs.readFileSync(tmpFilePath);
const blob_object = new Blob([file_buffer]);

Error: TypeError: Blob is not a constructor.

A workable solution would mean that upon writing code in my file, file.js, I would be able to run node file.js and console.log a Blob or File object. Does anyone know how this can be done in a series of steps? I'm on Node 8.

This will help you: https://stackoverflow.com/questions/14653349/node-js-can%C2%B4t-create-blobs — Kai Lehmann
– Kai Lehmann, Commented Jun 27, 2020 at 9:49
@KaiLehmann I also saw that post earlier too, but did not understand how the solutions given will solve my problem. They are either working with client side code or doing it via requests. — Prashin Jeevaganth
– Prashin Jeevaganth, Commented Jun 27, 2020 at 10:20
@SayanDey I still faced this problem when trying out the solution. However, I realised my client has a slightly different requirement so this situation could be avoided creating files from the node side — Prashin Jeevaganth
– Prashin Jeevaganth, Commented Jun 25, 2021 at 6:29

joe · Accepted Answer · 2022-10-21 13:46:14Z

6

As of writing, Blob support is still experimental, but this should work in recent versions of Node.js:

import fs from "fs";
import { Blob } from "buffer";

let buffer = fs.readFileSync("./your_file_name");
let blob = new Blob([buffer]);

So your second example should work if you upgrade Node to v16.

edited Oct 21, 2022 at 13:46

answered Apr 3, 2022 at 16:09

joe

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1 Comment

Bruno Lamps Over a year ago

This saved me. I lost 4 days trying to have a PersistenFile instance (from formidable package) appended to a FormData and sending it as a fetch api request. Buffer + Blob solved it.

lb90 · Accepted Answer · 2024-06-13 16:46:04Z

1

Node 19.8 has a new API for this: fs.openAsBlob(path, options)

See https://github.com/nodejs/node/issues/45188#issuecomment-1475017344

answered Jun 13, 2024 at 16:46

lb90

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