prototypes.js

if (!('filter' in Array.prototype)) {
  // conforms with the ECMA standard
  Array.prototype.filter = function filter(fn, thisArg) {
    var index = 0, length = this.length, value, returnValue = [], that = Object(this);
    for (; index < length; ++index) {
      if (index in that) {
        value = that[index];
        if (fn.call(thisArg, value, index, that)) {
          returnValue.push(value);
        }
      }
    }
    return returnValue;
  };
}

if (!('forEach' in Array.prototype)) {
  Array.prototype.forEach = function forEach(fn, thisArg) {
    var index = 0, length = this.length, that = Object(this), value;
    for (; index < length; ++index) {
      if (index in that) {
        value = that[index];
        fn.call(thisArg, value, index, that);
      }
    }
  };
}

if (!('map' in Array.prototype)) {
  Array.prototype.map = function map(fn, thisArg) {
    var newArray = [];

    this.forEach(function() {
      newArray.push(fn.apply(this, arguments));
    }, thisArg);

    return newArray;
  };
}

if (!('indexOf' in Array.prototype)) {
  Array.prototype.indexOf = function indexOf(needle, index) {
    index = Number(index);
    var length = this.length, that = Object(this);
    for (; index < length; ++index) {
      if (index in that && that[index] === needle) {
        return index;
      }
    }
    return -1;
  };
}

if (!('lastIndexOf' in Array.prototype)) {
  Array.prototype.lastIndexOf = function lastIndexOf(needle, index) {
    index = Number(index);
    var length = this.length, that = Object(this);
    for (; length-- >= index;) {
      if (length in that && that[length] === needle) {
        return index;
      }
    }
    return -1;
  };
}

if (!('reduce' in Array.prototype)) {
  Array.prototype.reduce = function reduce(fn) {
    var index, value, length = this.length, that = Object(this);
    if (arguments.length > 1) {
      index = 0;
      value = arguments[1];
    } else {
      index = 1;
      value = this[0];
    }

    for (; index < length; ++index) {
      if (index in that) {
        value = fn.call(this, value, that[index], index, this);
      }
    }
    return value;
  };
}

Array.prototype.count = function count(arg, thisArg) {
  if (typeof arg === "undefined") {
    return this.length;
  }

  if (arg.call) {
    return this.reduce(function(previous, current) {
      return previous + Number(!!arg.call(this, current));
    }, 0);
  }

  return this.reduce(function(previous, current) {
    return previous + Number(current === arg);
  }, 0);
};

Array.prototype.unique = function unique() {
  var lastValue, result;
  return this.sort().filter(function(value) {
    result = value !== lastValue;
    lastValue = result;
    return result;
  });
};

Array.prototype.compact = function compact() {
  var undefined;
  return this.filter(function(value) {
    return value !== null && value !== undefined;
  });
};

Array.prototype.reject = function reject(fn, thisArg) {
  return this.filter(function() {
    return !fn.apply(this, arguments);
  }, thisArg);
};

Array.prototype.last = function last() {
  return this[this.length - 1];
};

Array.prototype.select = Array.prototype.filter;
Array.prototype.append = Array.prototype.push;
Array.prototype.prepend = Array.prototype.unshift;