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JavaScript Code for Binary to Hexadecimal - Hexadecimal to Binary Conversion

By Stephen Bucaro

To be honest, you don't really need JavaScript to convert a binary number to a hexadecimal number. You simply go from right to left breaking the binary number into groups of four bits, and then use a binary to hexadecimal lookup table to replace each group with its respective hexadecimal digit.

Binary to Hexadecimal Table

0000	0
0001	1
0010	2
0011	3
0100	4
0101	5
0110	6
0111	7
1000	8
1001	9
1010	A
1011	B
1100	C
1101	D
1110	E
1111	F

However, if you must use JavaScript, say to create a web application, the code to convert a binary number to hexadecimal number is shown below.

<script>

var inBin = "111001100101";
var len = inBin.length;

// determine how many bits in first nibble
var firstBits = len % 4;

// if firstBits > 0 generate padding to make even nibbles
// increase len by number of padding bits
var inPadded = "";
if(firstBits > 0)
{
   var padding = "";
   for(var i = 0; i < 4 - firstBits; i++)
   {
     padding = "0" + padding;
     len++;
   }
   inPadded = padding + inBin;
}
else
{
inPadded = inBin;
}

// Binary to hexadecimal lookup table in
// a multidimensional array
var hexDigits = [
["0000","0"],
["0001","1"],
["0010","2"],
["0011","3"],
["0100","4"],
["0101","5"],
["0110","6"],
["0111","7"],
["1000","8"],
["1001","9"],
["1010","A"],
["1011","B"],
["1100","C"],
["1101","D"],
["1110","E"],
["1111","F"]];

// grab the input bits nibble by nibble
// look up in array and fetch hexadecimal value
var nibble = "";
var outHex = "";
for(var start = 0; start <= len - 4; start += 4)
{
   nibble = inPadded.substring(start, start + 4);
   for(var j = 0; j < hexDigits.length; j++)
   {
      if(nibble == hexDigits[j][0])
      {
          outHex += hexDigits[j][1];
      }
   }
}

alert(outHex);