課題を解くために作った。

cnv.js

/*
 * This program is licensed under the MIT License.
 * see: http://koba789.mit-license.org/
 *
 * node cnv.js 260
 */ 

var input = Number(process.argv[2] || 0);

var k,
    C = [];

for (k = 0; k < 10; ++k) { C.push(k.toString()); }
for (k = 0; k < 26; ++k) { C.push(String.fromCharCode(k + 65)); }


function convert (init, adic) {
  var result = [];

  var i = init,
      q = 0,
      m = 0,
      r = [];

  while (i !== 0) {
    q = ~~(i / adic);
    m = i % adic;
    r.push(C[m]);
    result.push(i.toString() + ' / ' + adic.toString() + ' = ' + q.toString() + ' ... ' + C[m]);
    i = q;
  }

  r.reverse();
  result.unshift(r.join(''));

  return result;
}

function indent (line) { return '    ' + line; }
function format (adic, rows) {
  rows[0] = adic.toString() + '進数: ' + rows[0];
  rows = rows.map(indent);
  rows[0] = rows[0].substring(2);
  return rows.join('\n');
}
function answer (input, adic) {
  return format(adic, convert(input, adic));
}

console.log(answer(input, 2));
console.log(answer(input, 10));
console.log(answer(input, 16));