<pre>
const keccak256V = require('js-sha3').keccak256;
const sha3_256 = require('js-sha3').sha3_256;

function toChecksumAddress (address) {
  address = address.toLowerCase().replace('0x', '')
  var hash = keccak256V(address);
  var ret = '0x'

  for (var i = 0; i < address.length; i++) {
    if (parseInt(hash[i], 16) >= 8) {
      ret += address[i].toUpperCase()
    } else {
      ret += address[i]
    }
  }

  return ret
}

/**
 * Checks if the given string is an address
 *
 * @method isAddress
 * @param {String} address the given HEX adress
 * @return {Boolean}
*/
var isAddress = function (address) {
    if (!/^(0x)?[0-9a-f]{40}$/i.test(address)) {
        // check if it has the basic requirements of an address
        return false;
    } else if (/^(0x)?[0-9a-f]{40}$/.test(address) || /^(0x)?[0-9A-F]{40}$/.test(address)) {
        // If it's all small caps or all all caps, return true
        return true;
    } else {
        // Otherwise check each case
        return isChecksumAddress(address);
    }
};

/**
 * Checks if the given string is a checksummed address
 *
 * @method isChecksumAddress
 * @param {String} address the given HEX adress
 * @return {Boolean}
*/
var isChecksumAddress = function (address) {
    // Check each case
    address = address.replace('0x','');
    //var addressHash = sha3(address.toLowerCase());
  var addressHash = sha3_256(address.toLowerCase());
    for (var i = 0; i < 40; i++ ) {
        // the nth letter should be uppercase if the nth digit of casemap is 1
        if ((parseInt(addressHash[i], 16) > 7 && address[i].toUpperCase() !== address[i]) || (parseInt(addressHash[i], 16) <= 7 && address[i].toLowerCase() !== address[i])) {
            return false;
        }
    }
    return true;
};

var originalAddress = "0x41b418a9bea5c6652a5fb6674370126e828b50fe"; 
var checkSumAddress = toChecksumAddress(originalAddress); 
console.log("checkSumAddress=" + checkSumAddress);

var isAddressResult = isAddress(originalAddress); 
console.log("isAddressResult=" + isAddressResult); 

</pre>

You can validate the address here:
https://tokenmarket.net/ethereum-address-validator