快排

 var arr = [1,8,9,3,7,5];
        function quickSort(obj) {
            if (obj.length <= 1) {
                return obj;
            }

            var num = Math.floor(obj.length/2),
                numValue = obj.splice(num,1);
            var left = [],
                right = [];
            for (var i = 0; i < obj.length; i++) {
                if (obj[i] < numValue) {
                    left.push(obj[i]);
                } else {
                    right.push(obj[i]);
                }
            }
            return quickSort(left).concat(numValue,quickSort(right));
        };
        console.log(quickSort(arr));