convert base64 to json in javaScript

Question

For example, I have a base64 code like this

const base64 = "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"

Now I want to convert this to json

I have tried to convert this base64 to object But I don't know if it's true or not but still my problem is not solved because I can't do anything with that json

const base64 = "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"

Convert to string using atob

let convertString = atob(base64);

Convert string to ArrayBuffer

let arrayBuffer = new ArrayBuffer(convertString.length);
let uint8Array = new Uint8Array(arrayBuffer);
for (let i = 0; i < convertString.length; i++) {
    uint8Array[i] = convertString.charCodeAt(i);
}

Now, using the pako library, it becomes an array that contains an object, but there is a space between all the characters, and this is very strange.

let inflatedData = pako.inflate(uint8Array, { to: 'string' });
console.log(inflatedData)

This is the image of the inflatedData console output

A point that might help: the data that comes from the database is typed as varBinary(Max).

Answer 1

This string is a little funky. It's JSON in UTF16-LE, gzipped, then base64 encoded. In Node:

const base64 = "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"

const zlib = require('zlib') // the builtin, not the old npm package
const buf = Buffer.from(base64, 'base64')
const res = zlib.gunzipSync(buf).toString('utf16le')

console.log(JSON.parse(res))

The result is an array of objects that look like test data.

---

Per the comments, here's how it could work in the browser. This assumes pako, which is mentioned in the question:

import pako from 'pako'
const gzipped = atob(base64)

const toU = (d) =>
    new Uint8Array([...d]
        .map((c) => c.charCodeAt(0)))

const utf16 = pako.inflate(toU(gzipped), { to: 'string' })
const td = new TextDecoder('utf-16le')
const res = td.decode(toU(utf16))

console.log(JSON.parse(res))

There might be a more efficient way to do this, but it's very late, so I'm not able to see it right now.