base-number-test.js

function convert_to(n, base) {
  if (base < 2 || base > 16) {
    throw new Error("Invalid base '" + base + "'. Base must be >= 2 or <= 16");
  }

  if (n === 0) {
    return 0;
  }

  var length = Math.floor(Math.log10(n) / Math.log10(base)) + 1;
  var result = Array.apply(null, Array(length));
  var remainder = n;

  for (var i = length; i > 0; --i) {
    result[i] = Math.floor(remainder % base);
    remainder /= base;
  }
  return result.join("");
}

function convert_from(str, base) {
  if (base < 2 || base > 16) {
    throw new Error("Invalid base '" + base + "'. Base must be >= 2 or <= 16");
  }

  var result = 0;
  var length = str.length;

  for (var i = length; i > 0; --i) {
    var value = +str.charAt(length - i);
    result += (value * Math.pow(base, i - 1));
  }
  return result;
}


function test_to(number, base, expected) {
  var actual = convert_to(number, base);
  var message = "should convert 'number=" + number + ", base=" + base + "' to '" + expected + "'";
  if (actual === expected) {
    console.log("  ok:", message);
  } else {
    console.log("fail:", message + " (actual: " + actual + ")");
  }
}

function test_from(str, base, expected) {
  var actual = convert_from(str, base);
  var message = "should convert 'str=" + str + ", base=" + base + "' to '" + expected + "'";
  if (actual === expected) {
    console.log("  ok:", message);
  } else {
    console.log("fail:", message + " (actual: " + actual + ")");
  }
}

test_to(294, 2, "100100110");
test_to(294, 4, "10212");
test_to(357, 7, "1020");
test_to(357, 16, "165");

test_from("100100110", 2, 294);
test_from("10212", 4, 294);
test_from("1020", 7, 357);
test_from("165", 16, 357);