caesar-cipher-mehdi/bin/caesar.js

Ceasar encrypt

#!/usr/bin/env node

/* Require on commander */

var program = require('commander');

/* Setting commander and the options */
program
  .usage("[option] <file...>")
  .option("-d <n>", "[number] [string...]")
  .parse(process.argv);

/* handle the -d option and check if the argument is valid and is the string to encode exist */
program
	.on("-d", function (number){
	  	var display = [];
	  	var string = program.args;
		if (number && program.args.length >= 1) {
			for (var i = 0; i <= string.length - 1; i++) {
				display.push(CaesarCrypto(number, string[i]));
			}
			display.forEach(function (str){
				console.log(str);
			});
		}
		else
			console.log ("Usage : bin/caesar.js -d [number] [string...]");
	})
	.parse(process.argv);


/* This function return the string encode or an error and takes 
an argument the number for the shift and the string to encode */ 
function CaesarCrypto(number, string){
	if (isNaN(number)){
		return "The shift for the caesar cryptography is not a number"
	}
	else if (!isNaN(string)) {
		return "The string contain contains only number";
	}
	else {
		number = parseInt(number);
		var ret = "";
		for (var i = 0;  i <= string.length - 1; i++) {
			var asciiCode = string.charCodeAt(i);
			if (asciiCode >= 65 && asciiCode <= 90 || asciiCode >= 97 && asciiCode <= 122) {
				if (asciiCode >= 65 && asciiCode <= 90 && asciiCode + number > 90 && number > 0)
					asciiCode = 64;
				else if (asciiCode >= 97 && asciiCode <= 122 && asciiCode + number > 122 && number > 0)
					asciiCode = 96;
				ret += String.fromCharCode(asciiCode + number % 26);
			}
			else
				ret += string.charAt(i);
		}
		return ret;
	}
}

module.exports = CaesarCrypto;