数组的insertAt

 var arr = [1, 3, 9, 6, 8];
            var insertAt = function(arr, index, value){
                var temp, temp1, length = arr.length;
                if (index >= 0 && index <= length) {
                    for (var i = 0, len = arr.length; i <= len; i++) {
                        if (i == index) {
                            temp = arr[i];
                            arr[i] = value;
                        }
                        else 
                            if (i > index) {
                                temp1 = arr[i];
                                arr[i] = temp;
                                temp = temp1;
                                
                            }
                    }
                }else{
                    alert('place pass the right parameter(between 0 and array length ) ');
                }
                               
            }
            insertAt(arr, -1, 5);