1 00:00:02,300 --> 00:00:04,250 So that were symbols, 2 00:00:04,250 --> 00:00:11,570 now let's move on to iterations and generators and let's start with iterators. An iterator is simply 3 00:00:11,660 --> 00:00:20,250 an object in the end which has a next method, which then in turn returns a result of a certain structure. 4 00:00:20,360 --> 00:00:28,940 For that let's say we have another constant, company and that holds an object where we have employees 5 00:00:29,150 --> 00:00:33,740 and there I got Max and I got Manu and I got Anna in there. 6 00:00:33,740 --> 00:00:36,440 Now this is a regular object, 7 00:00:36,440 --> 00:00:44,600 we make it iterable or we turn it into an iterator or you could say by adding a next method here 8 00:00:44,690 --> 00:00:46,700 which we can add like this, 9 00:00:46,700 --> 00:00:56,050 now the name has to be exactly next. Now in this next method here, we then should return an object where 10 00:00:56,050 --> 00:01:01,250 we have a value property, this could be employees 11 00:01:01,280 --> 00:01:04,190 this, employees zero 12 00:01:04,190 --> 00:01:10,670 so the first element in the employees array and a done property which simply signals with a boolean 13 00:01:10,990 --> 00:01:13,250 whether we got more values we can output or not. 14 00:01:14,180 --> 00:01:22,310 Well then we should probably also have another property here, current employee which initially is zero which 15 00:01:22,310 --> 00:01:25,920 we use to track which employee we already output 16 00:01:25,940 --> 00:01:34,640 so that here we can access this current employee and store that in a returned value variable or constant, I'm 17 00:01:34,640 --> 00:01:35,760 not going to change this 18 00:01:35,900 --> 00:01:42,920 and thereafter we can set this current employee to current employee plus one by incrementing it and then 19 00:01:42,920 --> 00:01:47,260 we return our value here. To be precise, 20 00:01:47,310 --> 00:01:53,730 we also want to check if we still have employees left through which we can loop by checking if this current 21 00:01:53,730 --> 00:01:58,990 employee is greater or equal than this employees length. 22 00:02:00,690 --> 00:02:05,430 We know if this is the case, then we're out of employees because we then have no more employees left, 23 00:02:06,090 --> 00:02:13,020 so here we could return a value of this current employee to return the number for which we failed and 24 00:02:13,020 --> 00:02:17,920 set done to true to signal that we are done looping through that. 25 00:02:18,010 --> 00:02:21,570 Now what's the idea behind this next method though? 26 00:02:21,570 --> 00:02:29,410 Well now we can console log company next and execute this a couple of times down there. 27 00:02:29,520 --> 00:02:32,240 If we save that and we reload, 28 00:02:32,240 --> 00:02:36,850 you see we print all different employees until we're done. 29 00:02:36,900 --> 00:02:42,780 So what we do here in the end is we create our own method that allows us to loop through a specific 30 00:02:42,780 --> 00:02:48,060 field of this object and we could have any looping logic we want in here. 31 00:02:48,060 --> 00:02:52,650 So this in the end kind of makes this a loopable object, 32 00:02:52,650 --> 00:02:58,650 right now we can't use it with for/of but we soon will be able to do so but we have an object where 33 00:02:58,650 --> 00:03:05,580 we have a method which we can call multiple times to go through any logic of our choice, in this case 34 00:03:05,580 --> 00:03:11,970 to go through all employees but of course it's totally up to you through which field or whatever you want 35 00:03:12,180 --> 00:03:13,890 to loop through here. 36 00:03:13,890 --> 00:03:19,260 So we have a method which we can call multiple times and every time it will return something different 37 00:03:19,590 --> 00:03:26,310 and not just that, it will actually go through some list of data, it will exhaust some list of data and 38 00:03:26,310 --> 00:03:32,520 when we exhausted that list, we'll not get an error, we'll simply get a response, we'll get back a value 39 00:03:32,700 --> 00:03:39,150 where we see that we're done because of this uniform return value where we always have a done property 40 00:03:39,210 --> 00:03:40,530 which is true or false, 41 00:03:40,560 --> 00:03:46,450 we also know if we can call next again and have more values left or if that's not the case. 42 00:03:46,740 --> 00:03:52,770 Now this alone as I said might not be totally helpful yet but this already is a logic you could use 43 00:03:52,770 --> 00:03:59,280 in some applications where you have an object which you use as a data storage and you want to go through 44 00:03:59,280 --> 00:04:04,110 some custom logic there to output some data which is stored in there, 45 00:04:04,110 --> 00:04:10,110 you don't want to use a for/in loop because you're maybe not interested in all the properties of this 46 00:04:10,110 --> 00:04:15,600 object but just in some of the values in one specific property of this object and then such a custom 47 00:04:15,600 --> 00:04:22,030 looping logic could be quite interesting here because what you could of course do with that is you could 48 00:04:22,030 --> 00:04:29,090 create a while loop and have a result here or let's say an employee 49 00:04:29,740 --> 00:04:40,690 and for that you call company next, then you have a while loop and as long as employee is not done, you 50 00:04:40,690 --> 00:04:46,630 continue looping and then you can console log employee value here or do whatever you want to do with 51 00:04:46,630 --> 00:04:51,180 it in the while loop and thereafter, set employee equal to company 52 00:04:51,220 --> 00:04:52,280 next again 53 00:04:52,420 --> 00:04:57,520 and now we have a dynamic loop, not a for/of loop but still a loop which will in the end go through 54 00:04:57,550 --> 00:05:00,170 all employees with our own iterator logic. 55 00:05:00,220 --> 00:05:06,280 So if we save that and we reload, it outputs the three employees we have and then it stops because then 56 00:05:06,490 --> 00:05:13,540 done is true and therefore this exit condition kicks in or this running condition is no longer true 57 00:05:13,750 --> 00:05:15,670 and therefore we make it out of that loop. 58 00:05:15,730 --> 00:05:21,700 So this would be one example how you can use your own iterator, company, which has this next method which 59 00:05:21,700 --> 00:05:27,640 then in turn allows you to have your own looping logic for whichever field or whichever logic related 60 00:05:27,640 --> 00:05:30,070 to this company object you might have.