How to read and write into file using JavaScript?

Question

Can anybody give some sample code to read and write a file using JavaScript?

Answer 1

Here is write solution for chrome v52+ (user still need to select a destination doe...)
source: StreamSaver.js

const writeStream = streamSaver.createWriteStream('filename.txt')
const encoder = new TextEncoder
let data = 'a'.repeat(1024)
let uint8array = encoder.encode(data + "\n\n")

writeStream.write(uint8array) // must be uInt8array
writeStream.close()

Best suited for writing large data generated on client side.
Otherwise I suggest using FileSaver.js to save Blob/Files