Node.js Buffer.from All In One

Node.js Buffer.from All In One

Buffer

Buffer.from

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from('buffer');
const buf2 = Buffer.from(buf1);

buf1[0] = 0x61;

console.log(buf1.toString());
// Prints: auffer
console.log(buf2.toString());
// Prints: buffer

https://nodejs.org/api/buffer.html#static-method-bufferfrombuffer

toString('base64')

buffer.atob(data)
Legacy. Use Buffer.from(data, 'base64') instead. ✅

buffer.btoa(data)
Legacy. Use buf.toString('base64') instead. ✅

https://nodejs.org/api/buffer.html#nodebuffer-module-apis

const convertImageToBase64URL = (filename, imageType = 'png') => {
  try {
    const buffer = fs.readFileSync(filename);
    // ❌ 二合一 Buffer.from(buffer, 'base64')
    const base64String = Buffer.from(buffer, 'base64');
    // console.log(`base64String`, base64String.slice(0, 100));
    return `data:image/${imageType};base64,${base64String}`;
  } catch (error) {
    throw new Error(`file ${filename} no exist ❌`)
  }
}

const convertImageToBase64URL = (filename, imageType = 'png') => {
  try {
    const buffer = fs.readFileSync(filename);
    // ✅ Buffer.from(buffer') + buffer.toString('base64');
    const base64String = Buffer.from(buffer).toString('base64');
    // console.log(`base64String`, base64String.slice(0, 100));
    return `data:image/${imageType};base64,${base64String}`;
  } catch (error) {
    throw new Error(`file ${filename} no exist ❌`)
  }
}

convertImageToBase64URL

Buffer.from

1. ES6 version

import fs from 'node:fs';

const convertImageToBase64URL = (filename, imageType = 'png') => {
  try {
    const buffer = fs.readFileSync(filename);
    const base64String = Buffer.from(buffer).toString('base64');
    // console.log(`base64String`, base64String.slice(0, 100));
    return `data:image/${imageType};base64,${base64String}`;
  } catch (error) {
    throw new Error(`file ${filename} no exist ❌`)
  }
}

export {
  convertImageToBase64URL,
};

// test cases
const ok = convertImageToBase64URL("./public/test.png");
const err = convertImageToBase64URL();

2. TypeScript version

import fs from 'node:fs';

type Filename = string;
type ImageType = 'png' | 'jpg' | 'jpeg' | 'gif' | 'webp';
type Base64String = `data:image/${ImageType};base64,${string}`;

const convertImageToBase64URL = (filename: Filename, imageType: ImageType = 'png'): Base64String => {
  try {
    const buffer = fs.readFileSync(filename);
    const base64String = Buffer.from(buffer).toString('base64');
    // console.log(`base64String`, base64String.slice(0, 100));
    return `data:image/${imageType};base64,${base64String}`;
  } catch (error) {
    throw new Error(`file ${filename} no exist ❌`)
  }
}

export {
  convertImageToBase64URL,
};

// test cases
const ok = convertImageToBase64URL("./public/test.png");
const err = convertImageToBase64URL();
/* 

Expected 1-2 arguments, but got 0.ts(2554)
An argument for 'filename' was not provided.
const convertImageToBase64URL: (filename: Filename, imageType?: ImageType) => Base64String

*/

3. fs.readFileSync {encoding: 'base64'}

const convertImageToBase64URL = (filename, imageType = 'png') => {
  try {
    const base64String = fs.readFileSync(filename, {
      encoding: 'base64',
    });
    console.log(`base64String`, base64String.slice(0, 100));
    return `data:image/${imageType};base64,${base64String}`;
  } catch (error) {
    throw new Error(`file ${filename} no exist ❌`)
  }
}

4. new Buffer

deprecated ⚠️ @deprecated — since v10.0.0 - Use Buffer.from(array) instead.

function base64_encode(file) {
  // read binary data
  var img = fs.readFileSync(file);
  console.log(`img`, img);
  // convert binary data to base64 encoded string
  return new Buffer(img).toString('base64');
}
/* 
The signature '(array: Uint8Array): Buffer' of 'Buffer' is deprecated.ts(6387)
buffer.d.ts(265, 16): The declaration was marked as deprecated here.
var Buffer: BufferConstructor
new (array: Uint8Array) => Buffer (+5 overloads)
Allocates a new buffer containing the given {array} of octets.

@param array — The octets to store.

@deprecated — since v10.0.0 - Use Buffer.from(array) instead.
*/

demos

pdf downloader crawler

const fs = require("fs");
var path = require("path");
const { exit } = require("process");

// axios
const axios = require("axios");

const log = console.log;

var folder = path.resolve(__dirname, '../pdf');
// log('folder', folder);
if (!fs.existsSync(folder)) {
  fs.mkdirSync(folder);
}

async function downloadPDF(url, filename) {
  log('🚧 pdf downloading ...');
  axios({
    method: 'get',
    url,
    responseType: 'arraybuffer',
    // responseType: 'stream',
    // responseType: 'document',
  })
  .then((response) => {
    console.log(`response`, response.data);
   // response <Buffer 25 50 44 46 2d 31 2e 34 0d 25 e2 e3 cf d3 0d 0a 35 35 20 30 20 6f 62 6a 0d 3c 3c 2f 4c 69 6e 65 61 72 69 7a 65 64 20 31 2f 4c 20 37 35 31 33 32 37 2f ... 751277 more bytes>
    // ✅
    let pdfBuffer = response.data;
    // ✅ 多此一举呀
    // let pdfBuffer = Buffer.from(response.data, 'binary');
    fs.writeFileSync(filename, pdfBuffer);
    log('✅ pdf finished!');
  });
}

const url = 'https://cs193p.sites.stanford.edu/sites/g/files/sbiybj16636/files/media/file/l1.pdf';
const filename = folder + '/cs193p-2021-l1.pdf';


log('filename =', filename);

downloadPDF(url, filename);

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Base64

TextEncoder & TextDecoder

function base64ToBytes(base64) {
  const binString = atob(base64);
  return Uint8Array.from(binString, (m) => m.codePointAt(0));
}

function bytesToBase64(bytes) {
  const binString = String.fromCodePoint(...bytes);
  return btoa(binString);
}

// Usage
bytesToBase64(new TextEncoder().encode("a Ā 𐀀 文 🦄"));
// "YSDEgCDwkICAIOaWhyDwn6aE"
new TextDecoder().decode(base64ToBytes("YSDEgCDwkICAIOaWhyDwn6aE"));
// "a Ā 𐀀 文 🦄"

https://developer.mozilla.org/en-US/docs/Web/API/TextEncoder

https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder

Converting arbitrary binary data

async function bytesToBase64DataUrl(bytes, type = "application/octet-stream") {
  return await new Promise((resolve, reject) => {
    const reader = Object.assign(new FileReader(), {
      onload: () => resolve(reader.result),
      onerror: () => reject(reader.error),
    });
    reader.readAsDataURL(new File([bytes], "", { type }));
  });
}

async function dataUrlToBytes(dataUrl) {
  const res = await fetch(dataUrl);
  return new Uint8Array(await res.arrayBuffer());
}

// Usage
await bytesToBase64DataUrl(new Uint8Array([0, 1, 2]));
// "data:application/octet-stream;base64,AAEC"
await dataUrlToBytes("data:application/octet-stream;base64,AAEC");
// Uint8Array [0, 1, 2]

https://developer.mozilla.org/en-US/docs/Glossary/Base64

ArrayBuffer

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer

https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer

refs

https://stackoverflow.com/questions/24523532/how-do-i-convert-an-image-to-a-base64-encoded-data-url-in-sails-js-or-generally/77342505#77342505

/Users/xgqfrms-mm/Documents/github/node-web-framework-all-in-one/000-xyz/express-sse/src/convert-image-tobase64-url.ts

https://github.com/xgqfrms/node-web-framework-all-in-one

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