/*** Array ***/

Array.prototype.random = function() {
    return this[Math.floor((Math.random()*this.length))];
};

Array.prototype.each = function(fun) {
    for(var i=0;i<this.length;i++) {
        fun(this[i]);
    }
};

Array.prototype.collect = function(fun) {
    var collect = [];
    for(var i=0;i<this.length;i++) {
        collect.push(fun(this[i]));
    }
    return collect;
};

Array.prototype.include = function(value) {
    for(var i=0;i<this.length;i++) {
        if(this[i] == value) {
            return true;
        }
    }
    return false;
};

/*** String ***/

String.prototype.valMatch = function(regex, expLength) {
    var key = this.match(regex);
    if(key !== null && key.length == expLength) {
        return key;
    } else {
        return false;
    }
};

String.prototype.endsWith = function(needle) {
    return needle === this.slice(this.length - needle.length);
};

String.prototype.startsWith = function(needle) {
    return needle === this.slice(0, needle.length);
};

String.prototype.distance = function(s1, s2) {
    // Calculate Levenshtein distance between two strings  
    // 
    // version: 1109.2015
    // discuss at: http://phpjs.org/functions/levenshtein    // +            original by: Carlos R. L. Rodrigues (http://www.jsfromhell.com)
    // +            bugfixed by: Onno Marsman
    // +             revised by: Andrea Giammarchi (http://webreflection.blogspot.com)
    // + reimplemented by: Brett Zamir (http://brett-zamir.me)
    // + reimplemented by: Alexander M Beedie    // *                example 1: levenshtein('Kevin van Zonneveld', 'Kevin van Sommeveld');
    // *                returns 1: 3
    if (s1 == s2) {
        return 0;
    } 
    var s1_len = s1.length;
    var s2_len = s2.length;
    if (s1_len === 0) {
        return s2_len;    }
    if (s2_len === 0) {
        return s1_len;
    }
     // BEGIN STATIC
    var split = false;
    try {
        split = !('0')[0];
    } catch (e) {        split = true; // Earlier IE may not support access by string index
    }
    // END STATIC
    if (split) {
        s1 = s1.split('');        s2 = s2.split('');
    }
 
    var v0 = new Array(s1_len + 1);
    var v1 = new Array(s1_len + 1); 
    var s1_idx = 0,
        s2_idx = 0,
        cost = 0;
    for (s1_idx = 0; s1_idx < s1_len + 1; s1_idx++) {        v0[s1_idx] = s1_idx;
    }
    var char_s1 = '',
        char_s2 = '';
    for (s2_idx = 1; s2_idx <= s2_len; s2_idx++) {        v1[0] = s2_idx;
        char_s2 = s2[s2_idx - 1];
 
        for (s1_idx = 0; s1_idx < s1_len; s1_idx++) {
            char_s1 = s1[s1_idx];            cost = (char_s1 == char_s2) ? 0 : 1;
            var m_min = v0[s1_idx + 1] + 1;
            var b = v1[s1_idx] + 1;
            var c = v0[s1_idx] + cost;
            if (b < m_min) {                m_min = b;
            }
            if (c < m_min) {
                m_min = c;
            }            v1[s1_idx + 1] = m_min;
        }
        var v_tmp = v0;
        v0 = v1;
        v1 = v_tmp;    }
    return v0[s1_len];
}

/*** Object ***/

Object.prototype.isFunction = function(obj) {
    return typeof(obj) === 'function';
};

Object.prototype.isArray = function(obj) {
    return Object.prototype.toString.call(obj) === '[object Array]';
};

/*** Integer ***/

Number.prototype.chanceIn = function(x, y) {
    var num = Math.floor(Math.random() * (y + 1)) / x;
    return num == 1;
};