008.js

// Find the greatest product of five consecutive digits in the 1000-digit number.

var number =
    '73167176531330624919225119674426574742355349194934' +
    '96983520312774506326239578318016984801869478851843' +
    '85861560789112949495459501737958331952853208805511' +
    '12540698747158523863050715693290963295227443043557' +
    '66896648950445244523161731856403098711121722383113' +
    '62229893423380308135336276614282806444486645238749' +
    '30358907296290491560440772390713810515859307960866' +
    '70172427121883998797908792274921901699720888093776' +
    '65727333001053367881220235421809751254540594752243' +
    '52584907711670556013604839586446706324415722155397' +
    '53697817977846174064955149290862569321978468622482' +
    '83972241375657056057490261407972968652414535100474' +
    '82166370484403199890008895243450658541227588666881' +
    '16427171479924442928230863465674813919123162824586' +
    '17866458359124566529476545682848912883142607690042' +
    '24219022671055626321111109370544217506941658960408' +
    '07198403850962455444362981230987879927244284909188' +
    '84580156166097919133875499200524063689912560717606' +
    '05886116467109405077541002256983155200055935729725' +
    '71636269561882670428252483600823257530420752963450';

function product(string, n, position) {
    var prod = 1;
    for (var i = position; i < (position+n); i++) {
        prod = prod * string.charAt(i);
    }
    return prod;
}

function greatestProduct(string, n) {
    var length = string.length;
    var max = 0;
    var newmax;
    for (var i = 0; i <= length - n; i++) {
        newmax = product(string, n, i);
        if (newmax > max) {
            max = newmax;
        }
    }
    return max;
}

console.log( greatestProduct(number, 5) );