Simple TOTP calculator in JS, use it at your own risk

totp.js

function sha1(data) {
    var K = [0x5A827999, 0x6ED9EBA1, 0x8F1BBCDC, 0xCA62C1D6];
    var H = [0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0];
    var words = [];
    var data_len = data.length;
    
    data.push(0x80);
    while (data.length % 64 !== 56) {
        data.push(0);
    }
    
    for (var i = 0; i < data.length; i += 4) {
        words.push((data[i] << 24) | (data[i + 1] << 16) | (data[i + 2] << 8) | data[i + 3]);
    }
    
    words.push(data_len * 8 / 0x100000000 |0);
    words.push(data_len * 8);

    for (var i = 0; i < words.length; i += 16) {
        var W = words.slice(i, i + 16);
        var a = H[0], b = H[1], c = H[2], d = H[3], e = H[4];
        
        for (var j = 0; j < 80; j++) {
            if (j >= 16) {
                W[j] = W[j - 3] ^ W[j - 8] ^ W[j - 14] ^ W[j - 16];
                W[j] = (W[j] << 1) | (W[j] >>> 31);
            }
            
            var s = (a << 5) | (a >>> 27);
            var f = 0;
            if (j < 20) f = (b & c) | (~b & d);
            else if (j < 40) f = b ^ c ^ d;
            else if (j < 60) f = (b & c) | (b & d) | (c & d);
            else f = b ^ c ^ d;
            
            var temp = (s + f + e + K[j / 20 |0] + W[j]) | 0;
            e = d;
            d = c;
            c = (b << 30) | (b >>> 2);
            b = a;
            a = temp;
        }
        
        H[0] = (H[0] + a) |0;
        H[1] = (H[1] + b) |0;
        H[2] = (H[2] + c) |0;
        H[3] = (H[3] + d) |0;
        H[4] = (H[4] + e) |0;
    }
    
    var hash = [];
    for (var i = 0; i < H.length; i++) {
        hash.push((H[i] >>> 24) & 0xFF, (H[i] >>> 16) & 0xFF, (H[i] >>> 8) & 0xFF, H[i] & 0xFF);
    }
    return hash;
}

function hmacSha1(key, data) {
    var block_size = 64;
    var o_key_pad = new Array(block_size);
    var i_key_pad = new Array(block_size);
    
    for (var i = 0; i < block_size; ++i) {
        o_key_pad[i] = 0x5C;
        i_key_pad[i] = 0x36;
    }
    
    for (var i = 0; i < key.length; ++i) {
        o_key_pad[i] ^= key[i];
        i_key_pad[i] ^= key[i];
    }
    
    return sha1(o_key_pad.concat(sha1(i_key_pad.concat(data))));
}
//
// Change the key and time step to meet your need
//
var key = [YOUR_KEY_IN_BYTES];
var now = new Date().getTime();
var t = now / 30000 |0;
var b = new Array(8);

while (key.length < 64) {
    key.push(0);
}

for (var i = 0; i < 8; ++i) {
    b[7 - i] = t & 0xFF;
    t >>>= 8;
}

var hash = hmacSha1(key, b);
var offset = hash[19] & 0x0f;
var hash2 = 0;

for (var i = 0; i < 4; ++i) {
    hash2 <<= 8;
    hash2 |= hash[offset + i];
}

hash2 &= 0x7FFFFFFF;
hash2 %= 1000000;

var totp = ("000000" + hash2).slice(-6);

if (typeof (WScript) !== 'undefined') {
  console = {
      log: function(msg) {
          WScript.Echo(msg);
      }
  };
}

console.log(totp);