how to convert a string containing utf8 hex codes to a javascript string

Question

I have a string that contains hexadecimal string (content of a utf8 string )

"666f6f6c 6973686e 6573732c 20697420 77617320 74686520 65706f63 68206f66 2062656c 6965662c 20697420 77617320 74686520 65706f63 68206f66 20696e63 72656475 6c697479 2c206974 20776173 20746865 20736561 736f6e20 6f66204c 69676874 2c206974 20776173 20746865 2073656"

I need to convert it back to a javascript string. how to do it?

Answer 1

var s = "666f6f6c 6973686e 6573732c 20697420 77617320 74686520 65706f63 68206f66 2062656c 6965662c 20697420 77617320 74686520 65706f63 68206f66 20696e63 72656475 6c697479 2c206974 20776173 20746865 20736561 736f6e20 6f66204c 69676874 2c206974 20776173 20746865 2073656";
var r = decodeURIComponent(s.replace(/\s+/g, '').replace(/[0-9a-f]{2}/g, '%$&'));

This solution actually handles UTF-8.

The idea is to put a % in front of every pair of hex digits (thus creating a URL encoded string), then letting decodeURIComponent handle the details (in particular, it will correctly decode multi-byte UTF-8 characters).

Answer 2

To properly handle UTF8 you may want to try this approach:

    function utf8ToHex(str) {
      return Array.from(str).map(c => 
        c.charCodeAt(0) < 128 ? c.charCodeAt(0).toString(16) : 
        encodeURIComponent(c).replace(/\%/g,'').toLowerCase()
      ).join('');
    },
    function hexToUtf8: function(hex) {
      return decodeURIComponent('%' + hex.match(/.{1,2}/g).join('%'));
    }

Demo: https://jsfiddle.net/lyquix/k2tjbrvq/

Answer 3

Node only solution. There's the Buffer class that can convert between data (eg utf bytes and utf8 strings.

Buffer.from(0x66, 0x6f, 0x6f, 0x6c).toString(); // 'fool'

So for your space-deliminated string format of bytes, you would:

let s = '666f6f6c 6973686e 6573732c';

// [102, 111, 111, 108, 105, 115, 104, 110, 101, 115, 115, 44]
let bytes = [...s.matchAll(/[^ ]{1,2}/g)].map(a => parseInt('0x' + a[0]));

Buffer.from(bytes).toString(); // 'foolishness,'

Answer 4

Use this:

function HexToString(s) {
  var escaped = "";
  var hex = "";
  if(s.length%4 > 0) {
    for (i = 0; i < (4 - (s.length % 4)); i++) {
      hex += "0";
    }
  }
  hex += s;
  for (var i = 0; i < hex.length; i += 4) {
    escaped += "%u" + hex.charAt(i) + hex.charAt(i + 1) + hex.charAt(i + 2) + hex.charAt(i + 3);
  }
  return unescape(escaped).split(unescape("%00")).join("");
}

It's works for me.