如何实现 hex2bin()？

Question

I need to communicate between Javascript and PHP (I use jQuery for AJAX), but the output of the PHP script may contain binary data. That's why I use bin2hex() and json_encode() on PHP side.

How do I convert the hexadecimal string in binary string, with JavaScript?

Answer 1

To answer your question:

function Hex2Bin(n){if(!checkHex(n))return 0;return parseInt(n,16).toString(2)}

Here are some further functions you may find useful for working with binary data:

//Useful Functions
function checkBin(n){return/^[01]{1,64}$/.test(n)}
function checkDec(n){return/^[0-9]{1,64}$/.test(n)}
function checkHex(n){return/^[0-9A-Fa-f]{1,64}$/.test(n)}
function pad(s,z){s=""+s;return s.length<z?pad("0"+s,z):s}
function unpad(s){s=""+s;return s.replace(/^0+/,'')}

//Decimal operations
function Dec2Bin(n){if(!checkDec(n)||n<0)return 0;return n.toString(2)}
function Dec2Hex(n){if(!checkDec(n)||n<0)return 0;return n.toString(16)}

//Binary Operations
function Bin2Dec(n){if(!checkBin(n))return 0;return parseInt(n,2).toString(10)}
function Bin2Hex(n){if(!checkBin(n))return 0;return parseInt(n,2).toString(16)}

//Hexadecimal Operations
function Hex2Bin(n){if(!checkHex(n))return 0;return parseInt(n,16).toString(2)}
function Hex2Dec(n){if(!checkHex(n))return 0;return parseInt(n,16).toString(10)}

Answer 2

JavaScript doesn't have support for binary data. Nevertheless you can emulate this with regular strings.

var hex = "375771", // ASCII HEX: 37="7", 57="W", 71="q"
    bytes = [],
    str;

for(var i=0; i< hex.length-1; i+=2){
    bytes.push(parseInt(hex.substr(i, 2), 16));
}

str = String.fromCharCode.apply(String, bytes);

alert(str); // 7Wq

Answer 3

function hex2bin(hex)
{
    var bytes = [], str;

    for(var i=0; i< hex.length-1; i+=2)
        bytes.push(parseInt(hex.substr(i, 2), 16));

    return String.fromCharCode.apply(String, bytes);    
}

thanks to Andris !

---

Other useful information about this topic (dex2bin,bin2dec) can be found here . According to that, here is a bin2hex solution:

parseInt(1100,2).toString(16); //--> c

Answer 4

Although not an answer to the actual question, it is perhaps useful in this case to also know how to reverse the process:

function bin2hex (bin)
{

  var i = 0, l = bin.length, chr, hex = ''

  for (i; i < l; ++i)
  {

    chr = bin.charCodeAt(i).toString(16)

    hex += chr.length < 2 ? '0' + chr : chr

  }

  return hex

}

As an example, using hex2bin on b637eb9146e84cb79f6d981ac9463de1 returns ¶7ëFèL·mÉF=á , and then passing this to bin2hex returns b637eb9146e84cb79f6d981ac9463de1 .

It might also be useful to prototype these functions to the String object:

String.prototype.hex2bin = function ()
{

  var i = 0, l = this.length - 1, bytes = []

  for (i; i < l; i += 2)
  {
    bytes.push(parseInt(this.substr(i, 2), 16))
  }

  return String.fromCharCode.apply(String, bytes)   

}

String.prototype.bin2hex = function ()
{

  var i = 0, l = this.length, chr, hex = ''

  for (i; i < l; ++i)
  {

    chr = this.charCodeAt(i).toString(16)

    hex += chr.length < 2 ? '0' + chr : chr

  }

  return hex

}

alert('b637eb9146e84cb79f6d981ac9463de1'.hex2bin().bin2hex())

Answer 5

All proposed solutions use String.fromCharCode , why not simply using unescape ?

String.prototype.hex2bin = function()
{ 
   var i = 0, len = this.length, result = "";

   //Converting the hex string into an escaped string, so if the hex string is "a2b320", it will become "%a2%b3%20"
   for(; i < len; i+=2)
      result += '%' + this.substr(i, 2);      

   return unescape(result);
}

and then:

alert( "68656c6c6f".hex2bin() ); //shows "hello"

Answer 6

With reference to node.js ( not in browser ).

Basically it's all over-engineered and does not work well.

responses are out of alignment and though text-wise they are the same bit wise everything is all over the place :

curl http://phpimpl.domain.com/testhex.php | xxd

00000000: de56 a735 4739 c01d f2dc e14b ba30 8af0  .Q.%G9.....;.0..

curl http://nodejs.domain.com/ | xxd

00000000: c39e 56c2 a725 4739 c380 c3ad c3b1 c39c  ..Q..%G9........
00000010: c3a1 37c2 6b30 c28f c3b0                 ..;..0....

The proper way to implement this in node is :

function hex2bin(hex){
   return new Buffer(hex,"hex");
}


curl http://nodejs.domain.com/ | xxd

00000000: de56 a735 4739 c01d f2dc e14b ba30 8af0  .Q.%G9.....;.0..

Hope this helps.

Answer 7

Here is an implementation of hex2bin in JS that takes a string and returns Uint8Array, works both in browsers and nodejs,

function hex2bin(hex) {
  var length = hex.length / 2;
  var result = new Uint8Array(length);
  for (var i = 0; i < length; ++i) {
    result[i] = parseInt(hex.slice(i * 2, i * 2 + 2), 16);
  }
  return result;
}

And its inverse,

function bin2hex(bin) {
  return Array.from(bin).map(function (x) {
    return x.toString(16).padStart(2, '0');
  }).join('');
}

Answer 8

JavaScript does actually contain support for binary data. See Uint8Array .

Just read each byte from the array and convert it into hexadecimal.

Answer 9

If someone needs the other direction (bin to hex), here is it:

function bin2hex(bin) {
    return new Buffer(bin).toString("hex");
}