sort.js

var sort = (function () {
    function defCompare(a, b) {
        var aStr = String(a),
            bStr = String(b);
        
        if (aStr > bStr) {
            return 1;
        }
        else if (aStr < bStr) {
            return -1;
        }
        else {
            return 0;
        }
    }
    
    function isSorted(arr, compareFunc) {
        if (typeof compareFunc == 'undefined') {
            compareFunc = defCompare;
        }
        for (var i = 1, len = arr.length; i < len; i++) {
            if (compareFunc(arr[i - 1], arr[i]) > 0) {
                return false;
            }
        }
        return true;    
    }
    
    return function (arr, compareFunc) {
        if (!isSorted(arr, compareFunc)) {
            return arr.slice().sort(compareFunc);
        }
        
        return arr.slice();
    }    
})();


function comparator(a, b) {
    return a - b;
}

var arr = [];
for (var i = 0; i < 1e6; i++) {
    arr.push(i);
}

var time = new Date();
sort(arr, comparator);
time = new Date() - time;
console.log(time);

var time = new Date();
arr.sort(comparator);
time = new Date() - time;
console.log(time);