ECMAScript 5 implementation of Python's range function

Array.range.js

/**
 * ECMAScript 5 implementation of Python's range function.
 * @see {@link http://docs.python.org/release/1.5.1p1/tut/range.html}
 * @param {Number} start
 * @param {Number} end
 * @param {Number} step
 * @param {Boolean} includeEndpoint
 * @return {Array}
 */
Object.defineProperty(Array, "range", {
    writable: false, configurable: false, enumerable: true,
    value: function(start, end, step, includeEndpoint) {
        var length = start;

        step = step === undefined? 1: step;

        if (arguments.length == 1) {
            start = 0;
        } else {
            length = Math.ceil((end-start)/step);
        }

        var current = start;
        var array = (new Array(length + ((includeEndpoint||false)?1:0))).join("|").split("|");

        return array.map(function() {
            var value = current;

            current += step;
        
            return value;
        });
    }
});

sample.js

console.log(Array.range(10));
//[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

//The given end point is never part of the generated list; Array.range(10) generates a list of 10 values,
//exactly the legal indices for items of a sequence of length 10. It is possible to let the range start
//at another number, or to specify a different increment (even negative): 

console.log(Array.range(5, 10))
//[5, 6, 7, 8, 9]
console.log(Array.range(0, 10, 3))
//[0, 3, 6, 9]
console.log(Array.range(-10, -100, -30))
//[-10, -40, -70]

//To iterate over the indices of a sequence, combine range() and the length property, as follows: 

var a = ['Mary', 'had', 'a', 'little', 'lamb'];

for (var i in Array.range(a.length)) {
    console.log(i, a[i]);
}

//0 Mary
//1 had
//2 a
//3 little
//4 lamb