Bruteforcing the self-descriptive number.

bruteforce-self-descriptive.js

/*jslint node: true */
'use strict';

//Initialize vars
var value = '00000';
var int = 0;
var finalString =  "";

//Main code
while(!selfDescripting(value)){
    value = increment(value);
    console.log(value);
}
console.log(value, "Gotcha !");

//Guess it doesn't require doc... Just increment and add missing zeroes
function increment(toIncrement){
    int = parseInt(toIncrement, 10);
    ++int;
    finalString = ""+int;
    while(finalString.length !== value.length){
        finalString = "0" + finalString;
    }
    return finalString;
}

/**
 * Tells wether or not a number is self-descripting.
 * This means first digit is the number of 0 in the number, second the number of 1, ...
 * @param {string} toCheck - string of the number to check.
 * @return {boolean} true if number is self-descripting. Otherwise, false.
 */
 function selfDescripting(toCheck){
     var array = toCheck.split('');
     var returns = true;
     array.forEach(function (current, i){
         var int = parseInt(current, 10);
         if(int !== amountOf(i+'', toCheck)){
             returns =  false;
         }
     });
     return returns;
 }

/**
 * Amount of character in a string.
 * @param {string} char - Char to check for. Can only be 1 length.
 * @param {string} inString - string to check for char.
 * @return {number} Amount of char in inString.
 */
function amountOf(char, inString){
    var amount = 0;
    for(var i=0; i<inString.length; ++i){
        if(inString[i] === char){
            amount++;
        }
    }
    return amount;
}