[JavaScript] Download base64 encoded file within a browser

            const sBase64 = "JVBERi0xLjQKJcOkw7zDtsOfCjIgMCBvYmoKPDwvTGVuZ3....."
            const arrayBuffer = new Uint8Array([...window.atob(sBase64)].map(char => char.charCodeAt(0)))
            const fileLink = document.createElement('a')

            fileLink.href = window.URL.createObjectURL(new Blob([arrayBuffer]))
            fileLink.setAttribute('download', "example.pdf")
            document.body.appendChild(fileLink)
            fileLink.click()

Or use the npm package FileSaver.

import { saveAs } from "file-saver";

const sBase64 = "JVBERi0xLjQKJcOkw7zDtsOfCjIgMCBvYmoKPDwvTGVuZ3....."
const buffer = Buffer.from(sBase64, "base64")
saveAs(new Blob([buffer]), "example.pdf")