num2word - JoeSimmons/tenfold

// num2word by JoeSimmons
var num2word = (function () {
    'use strict';
    var  ones = {
            '0' : 'zero', '1' : 'one', '2' : 'two', '3' : 'three',
            '4' : 'four', '5' : 'five', '6' : 'six', '7' : 'seven',
            '8' : 'eight', '9' : 'nine'
        },
        _10_19 = {
            '10' : 'ten', '11' : 'eleven', '12' : 'twelve', '13' : 'thirteen',
            '14' : 'fourteen', '15' : 'fifteen', '16' : 'sixteen',
            '17' : 'seventeen', '18' : 'eighteen', '19' : 'nineteen'
        },
        tens = {
            '2' : 'twenty', '3' : 'thirty', '4' : 'forty', '5' : 'fifty',
            '6' : 'sixty', '7' : 'seventy', '8' : 'eighty', '9' : 'ninety'
        };

    return function (num) {
        var word = '', char0, nstr, rest;

        if ( isNaN( parseInt(num, 10) ) ) { return '(error - invalid argument)'; }

        nstr = (num + '').split('.')[0].replace(/^0+(\d+)/, '$1'); // format the number and make it a string
        num = parseInt(nstr, 10); // get a number, even if it's a string
        rest = nstr.substring(1); // cache the characters past the first to be used later
        char0 = nstr.charAt(0); // make an array of characters

        if (num < 10) {               // 0 - 9
            word = ones[char0];
        } else if (num < 20) {        // 10 - 19
            word = _10_19[nstr];
        } else if (num < 100) {       // 20 - 99
            word = tens[char0] + '-' + num2word(rest);
        } else if (num < 1000) {      // 100 - 999
            word = ones[char0] + ' hundred ' + num2word(rest);
        } else if (num < 1000000) {   // 1,000 - 999,999
            word = num2word( nstr.slice(0, -3) ) + ' thousand ' + num2word( nstr.slice(-3) );
        } else {
            return '(error - number too large)';
        }

        return word.replace(/[ -]zero/g, '');
    };
}());