Can't fit file encoding when working with Chrome File System API

Question

I need to read a file which contains a group of symbols moved 65 in ASCII table. It means, for each symbol I am meant to do:

String.fromCharCode(\'¢\'.charCodeA         


        

Answer 1

Problem is, your shifted text is no longer text by readAsText criteria. Trying to read it with any standard codepage is not going to work.

You should read the file as binary with readAsArrayBuffer(), interpret it as unsigned 8-bit int array, shift the bytes, and then convert the result to string.

var buf = new Uint8Array(reader.readAsArrayBuffer(file));
buf = buf.map((byte) => byte-65);
var string = new TextDecoder("ascii").decode(buf);