如何在Javascript中将十六进制字符串转换为字节，将字节转换为十六进制字符串？

Question

How do you convert a hex code represented in a string to a byte and the reverse in Javascript?

var conv = require('binstring');
var hexstring ='80';
var bytestring = conv(hexstring, {in:'hex', out:'utf8'});
var backtohexstring = conv(bytestring, {in:'utf8', out:'hex'}); // != '80'???

backtohexstring decodes an incoming data string to the correct hex (I also used utf8 vs. byte, because it 'looked' like the incoming string when printed to the console), so I'm confused...

I also found these two native javascript functions, the decoder works on my incoming stream, but I still can't get the hex to encode...

function encode_utf8( s ) {
  return unescape( encodeURIComponent( s ) );
}
function decode_utf8( s ) {
  return decodeURIComponent( escape( s ) );
}

Answer 1

Here's a node.js specific approach, taking advantage of the the Buffer class provided by the node standard lib.

https://nodejs.org/api/buffer.html#buffer_buffers_and_character_encodings

To get the byte (0-255) value:

Buffer.from('80', 'hex')[0];
// outputs 128

And to convert back:

Buffer.from([128]).toString('hex');
// outputs '80'

To convert to utf8:

Buffer.from('80', 'hex').toString('utf8');

Answer 2

You can make use of Number.prototype.toString and parseInt .

The key is to make use of the radix parameters to do the conversions for you.

var bytestring = Number('0x' + hexstring).toString(10);    // '128'
parseInt(bytestring, 2).toString(16);  // '80'

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