Array.max() Method

array-max.js

/**
 * Get the maximum value from array.
 * @param getter Optional function for mapping array elements to actual comparison value.
 * Examples:
 *    lengths.max();
 *    persons.max(function(person) { return person.age; });
 */
Array.prototype.max = function(getter) {
    var val;
    getter = getter || function(v) { return v; }
    return this.reduce(function(cur, el) {
        val = getter(el);
        return (typeof cur == "undefined") || val > cur ? val : cur;
    }, undefined);
};