How to convert from Hex to ASCII in JavaScript?

I found a useful function present in web3 library.

var hexString = "0x1231ac"
string strValue = web3.toAscii(hexString)

Update: Newer version of web3 has this function in utils

The functions now resides in utils:

var hexString = "0x1231ac"
string strValue = web3.utils.hexToAscii(hexString)

** for Hexa to String**

let input  = '32343630';

Note : let output = new Buffer(input, 'hex'); // this is deprecated

let buf = Buffer.from(input, "hex");
let data = buf.toString("utf8");

I've found that the above solution will not work if you have to deal with control characters like 02 (STX) or 03 (ETX), anything under 10 will be read as a single digit and throw off everything after. I ran into this problem trying to parse through serial communications. So, I first took the hex string received and put it in a buffer object then converted the hex string into an array of the strings like so:

buf = Buffer.from(data, 'hex');
l = Buffer.byteLength(buf,'hex');
for (i=0; i<l; i++){

    char = buf.toString('hex', i, i+1);
    msgArray.push(char);

}

Then .join it

message = msgArray.join('');

then I created a hexToAscii function just like in @Delan Azabani's answer above...

function hexToAscii(str){
    hexString = str;
    strOut = '';
        for (x = 0; x < hexString.length; x += 2) {
            strOut += String.fromCharCode(parseInt(hexString.substr(x, 2), 16));
        }
    return strOut;    
}

then called the hexToAscii function on 'message'

message = hexToAscii(message);

This approach also allowed me to iterate through the array and slice into the different parts of the transmission using the control characters so I could then deal with only the part of the data I wanted. Hope this helps someone else!

An optimized version of the implementation of the reverse function proposed by @michieljoris (according to the comments of @Beterraba and @Mala):

function a2hex(str) {
  var hex = '';
  for (var i = 0, l = str.length; i < l; i++) {
    var hexx = Number(str.charCodeAt(i)).toString(16);
    hex += (hexx.length > 1 && hexx || '0' + hexx);
  }
  return hex;
}
alert(a2hex('2460')); // display 32343630