1 00:00:02,150 --> 00:00:04,160 So now we added guards. 2 00:00:04,160 --> 00:00:06,850 We leave aside the fact that we have a bunch of 3 00:00:06,850 --> 00:00:10,170 if statements here, we should see another problem 4 00:00:10,170 --> 00:00:12,060 with this code though. 5 00:00:12,060 --> 00:00:16,150 And that is the mixture of levels of abstraction. 6 00:00:16,150 --> 00:00:19,050 What we learned about functions still applies. 7 00:00:19,050 --> 00:00:22,310 This is inside of a functional after all. 8 00:00:22,310 --> 00:00:25,880 And when it comes to simplifying controlled structures 9 00:00:25,880 --> 00:00:29,210 and managing deeply nested controlled structures, 10 00:00:29,210 --> 00:00:33,660 splitting up functions and extracting controlled structures 11 00:00:33,660 --> 00:00:37,103 into functions is another important building block. 12 00:00:37,970 --> 00:00:41,210 Now this starts with the checks here. 13 00:00:41,210 --> 00:00:44,190 We can run the checks here in line 14 00:00:44,190 --> 00:00:47,720 but we could also outsource this into a separate function 15 00:00:47,720 --> 00:00:52,420 which then also would allow us to use positive wording. 16 00:00:52,420 --> 00:00:55,080 For example, here we are interested in whether 17 00:00:55,080 --> 00:00:57,460 we have transactions or not. 18 00:00:57,460 --> 00:01:00,390 So we could grab this code, cut it 19 00:01:00,390 --> 00:01:02,180 and add a new function 20 00:01:02,180 --> 00:01:05,570 below this process transactions function. 21 00:01:05,570 --> 00:01:07,827 And we could name this function isEmpty 22 00:01:09,610 --> 00:01:12,500 and then simply return the result of this check 23 00:01:12,500 --> 00:01:16,363 of course ensure though that we get transactions as a value. 24 00:01:17,669 --> 00:01:19,920 So isEmpty will return true 25 00:01:19,920 --> 00:01:22,130 if we have no transactions object 26 00:01:22,130 --> 00:01:24,963 or if we have no elements in transactions. 27 00:01:25,840 --> 00:01:30,840 And I named this is empty and not has no elements 28 00:01:31,710 --> 00:01:35,140 because of this prefer positive checks rule here, 29 00:01:35,140 --> 00:01:39,320 it's simply is easier to read if we use a positive statement 30 00:01:39,320 --> 00:01:40,830 than a negative one. 31 00:01:40,830 --> 00:01:42,910 So if I named this is empty, 32 00:01:42,910 --> 00:01:46,760 I can simply check here in process transactions, 33 00:01:46,760 --> 00:01:50,663 if isEmpty transactions, 34 00:01:51,700 --> 00:01:53,660 passing transactions to isEmpty. 35 00:01:53,660 --> 00:01:55,410 And this is super easy to read. 36 00:01:55,410 --> 00:01:58,323 If it's empty transactions, then we do this. 37 00:01:59,300 --> 00:02:02,870 Now of course, speaking of mixed levels of abstraction, 38 00:02:02,870 --> 00:02:06,100 we do have more violations of that rule. 39 00:02:06,100 --> 00:02:09,100 For example, also in this console log statement, 40 00:02:09,100 --> 00:02:12,170 it's not directly related to the if statement 41 00:02:12,170 --> 00:02:14,440 and to simplifying the if statements 42 00:02:14,440 --> 00:02:17,060 but of course we might also wanna extract that 43 00:02:17,060 --> 00:02:19,490 so we can grab this console log statement 44 00:02:19,490 --> 00:02:21,600 and add a number of function here, 45 00:02:21,600 --> 00:02:26,010 showErrorMessage could be the function name 46 00:02:26,010 --> 00:02:28,790 where we get the message as a parameter 47 00:02:28,790 --> 00:02:32,660 and where we then simply output the message like this 48 00:02:32,660 --> 00:02:37,460 and then we could call, showErrorMessage here 49 00:02:37,460 --> 00:02:40,700 and forward this message which we wanna show to again 50 00:02:40,700 --> 00:02:44,150 have an equal level of abstraction here. 51 00:02:44,150 --> 00:02:46,600 Now of course, extracting these two functions 52 00:02:46,600 --> 00:02:48,430 didn't remove the if statement, 53 00:02:48,430 --> 00:02:51,370 it also didn't shorten this code here 54 00:02:51,370 --> 00:02:53,660 but it makes it a bit more readable 55 00:02:53,660 --> 00:02:57,130 and overall that is our end goal still. 56 00:02:57,130 --> 00:03:00,430 Nonetheless, when we talk about functions, 57 00:03:00,430 --> 00:03:03,870 it's not just about extracting Boolean checks 58 00:03:03,870 --> 00:03:07,610 and deriving booleans or showing messages, 59 00:03:07,610 --> 00:03:11,550 it's also about extracting entire controlled structures 60 00:03:11,550 --> 00:03:12,760 from our code. 61 00:03:12,760 --> 00:03:15,210 And that's therefore what we're going to do next.