1 00:00:00,860 --> 00:00:07,560 All right guys so we briefly talked about symbols back in the data types lecture back in the I think 2 00:00:07,560 --> 00:00:12,750 it was the second section very very briefly we didn't even really talk about what they were we just 3 00:00:12,750 --> 00:00:16,250 established that they were in fact a primitive data type. 4 00:00:16,530 --> 00:00:16,980 OK. 5 00:00:16,980 --> 00:00:19,650 And they're part of the ESX standard. 6 00:00:19,650 --> 00:00:23,830 So let's go ahead and experiment a little bit with symbols. 7 00:00:23,850 --> 00:00:28,970 So I have my index each team and we're just linking to an app J.S. file which is completely empty. 8 00:00:28,980 --> 00:00:36,540 I have it open over here in my browser and the unique thing about symbols is that every single one is 9 00:00:36,540 --> 00:00:37,850 completely unique. 10 00:00:37,860 --> 00:00:43,470 And this makes them very valuable in terms of things like object property identifiers. 11 00:00:43,470 --> 00:00:44,770 And this is the main sim. 12 00:00:44,790 --> 00:00:48,230 The main purpose of symbols is their uniqueness. 13 00:00:48,420 --> 00:00:52,580 So let's go ahead and create a symbol. 14 00:00:52,580 --> 00:00:52,940 All right. 15 00:00:52,950 --> 00:01:00,480 So we can create a variable say Constable call it on and we're going to set it equal to symbol just 16 00:01:00,480 --> 00:01:01,360 like that. 17 00:01:01,360 --> 00:01:01,710 All right. 18 00:01:01,740 --> 00:01:03,980 Now it's not new symbol. 19 00:01:04,320 --> 00:01:09,950 OK we'll get an error because there's no constructor it's an actual primitive value. 20 00:01:10,170 --> 00:01:14,240 OK we can also add an identifier inside of our symbol if we want. 21 00:01:14,240 --> 00:01:20,920 So right here we want to say like CYM to assume to set this variable the same too. 22 00:01:21,330 --> 00:01:30,530 And if we go ahead and console da log say Sim one it's just going to simply give us symbol we logs to 23 00:01:30,570 --> 00:01:31,710 It'll give us symbol. 24 00:01:31,710 --> 00:01:33,980 Along with that identifier. 25 00:01:34,020 --> 00:01:34,310 All right. 26 00:01:34,320 --> 00:01:41,150 Now if we want to look at the type we can say type is the type of operator and that gives a symbol. 27 00:01:41,250 --> 00:01:44,180 OK so this is this. 28 00:01:44,190 --> 00:01:47,420 This tells us that this is a primitive data value. 29 00:01:48,430 --> 00:01:52,060 So it doesn't return the type object or anything like that. 30 00:01:52,060 --> 00:01:58,210 It's a pure primitive value which is symbol all right or pure pin primitive type. 31 00:01:58,270 --> 00:02:00,820 Now no two symbols can be the same. 32 00:02:00,820 --> 00:02:16,700 So even if we were to do even if we were to do it say console got log in let's say symbol equal to symbol. 33 00:02:17,090 --> 00:02:17,530 OK. 34 00:02:17,560 --> 00:02:20,270 So if we do that we say we're going to get false. 35 00:02:20,450 --> 00:02:20,770 OK. 36 00:02:20,770 --> 00:02:24,490 Because they can never equal they can never be the same. 37 00:02:24,510 --> 00:02:30,870 Even if we put the same identifier in here let's say 1 to 3 and say. 38 00:02:30,910 --> 00:02:33,420 Still false. 39 00:02:33,460 --> 00:02:42,400 All right if we were to try to use a symbol inside of a string like if we were to put to use tactics 40 00:02:42,400 --> 00:02:48,060 here and we'll just say hello and we'll put in the sim one variable. 41 00:02:48,130 --> 00:02:53,350 If we go ahead and run that we're going to get cannot convert symbol value to a string but if we wanted 42 00:02:53,350 --> 00:02:56,740 to we could wrap it in the string function 43 00:03:00,080 --> 00:03:02,560 subseries string should be in here. 44 00:03:05,630 --> 00:03:06,650 So it could go like that. 45 00:03:06,680 --> 00:03:08,780 We'll get the helo symbol. 46 00:03:08,780 --> 00:03:11,870 You could also do if you don't want to wrap it in the string. 47 00:03:11,870 --> 00:03:17,180 I mean there's not too many reasons you do this but just to show you can you can also do two string 48 00:03:17,180 --> 00:03:20,140 like that and that'll work. 49 00:03:20,160 --> 00:03:30,980 All right Snell's to get into them one of the main reasons for symbols and that is unique object keys. 50 00:03:30,980 --> 00:03:31,310 All right. 51 00:03:31,320 --> 00:03:44,290 So if we were to create let's say key one and set this equal to symbol Hamil's say Konst key to and 52 00:03:44,610 --> 00:03:51,160 set that to symbol even give this one an ID of sim too. 53 00:03:51,180 --> 00:03:51,540 All right. 54 00:03:51,550 --> 00:03:55,370 I'm just going to comment those. 55 00:03:55,440 --> 00:03:55,740 All right. 56 00:03:55,740 --> 00:04:03,330 And then what we could do is create an object so will say my object set that to an object and then we 57 00:04:03,330 --> 00:04:05,430 can add these keys. 58 00:04:05,430 --> 00:04:05,750 All right. 59 00:04:05,760 --> 00:04:12,030 Now whenever you want to use a variable as a key you don't want to go like this. 60 00:04:12,030 --> 00:04:21,870 Key one equals oh say prop 1 because what it's doing is it's just looking at this as a normal property. 61 00:04:21,870 --> 00:04:28,120 All right if you want to use an actual variable then you want to use the brackets syntax like this. 62 00:04:28,120 --> 00:04:32,890 All right so that first one was not using this variable I was just using. 63 00:04:32,940 --> 00:04:39,450 Key one is a property in this case we're using the actual symbol as a property. 64 00:04:39,570 --> 00:04:47,600 All right and if we wanted to create another one we could do the two and said that as Prop 2. 65 00:04:47,610 --> 00:04:49,590 All right and if we console log 66 00:04:52,560 --> 00:05:06,320 I will do my OB stot are not dog key one and save and we have prop one if we console log by August 2 67 00:05:06,350 --> 00:05:08,720 we should get Proc. to. 68 00:05:09,420 --> 00:05:09,750 All right. 69 00:05:09,750 --> 00:05:16,910 So there are some things that that work a little different with symbols for one. 70 00:05:17,040 --> 00:05:26,550 If we were to loop through my obs using for n then it wouldn't actually show up in the iteration because 71 00:05:26,550 --> 00:05:29,520 they're not enumerable in four in iteration. 72 00:05:29,520 --> 00:05:33,740 So let me show you what I mean some of these symbols are not 73 00:05:36,470 --> 00:05:41,040 numerable in 4. 74 00:05:41,360 --> 00:05:44,030 So if we were to say for 75 00:05:46,780 --> 00:05:57,530 let's say for let I in my age and then what I wanted to do before I do anything here I'm going to go 76 00:05:57,530 --> 00:06:03,590 ahead and just add to the my object but not using a symbol I'm just going to say my object Daut will 77 00:06:03,590 --> 00:06:05,020 call it key 3. 78 00:06:05,150 --> 00:06:11,910 But remember this isn't a symbol it's just a simple property and we'll set that to prop 3. 79 00:06:12,190 --> 00:06:16,280 And let's say my AABs Daut key four equals 80 00:06:19,480 --> 00:06:20,330 four. 81 00:06:20,600 --> 00:06:29,300 So down here we'll go ahead and console log and let's get the key and the value so I will give us the 82 00:06:29,300 --> 00:06:29,770 key. 83 00:06:29,770 --> 00:06:37,430 I'm going to put some back ticks in here and will say I which will give us the key and then to get the 84 00:06:37,430 --> 00:06:41,790 value we'll say my age. 85 00:06:42,410 --> 00:06:45,520 I think that will save. 86 00:06:45,770 --> 00:06:49,310 Actually we need to get rid of these console's and save. 87 00:06:49,490 --> 00:06:55,300 And now you see we just get T3 and key for OK we're looping through this. 88 00:06:55,320 --> 00:07:01,330 The my obs which has all of these in it the two symbols and the two regular properties. 89 00:07:01,460 --> 00:07:07,610 Yet only the two regular properties are showing up here because symbols again are not enumerable for 90 00:07:07,910 --> 00:07:09,490 in for in loops. 91 00:07:09,530 --> 00:07:10,140 OK. 92 00:07:10,370 --> 00:07:18,000 So just remember that another thing is that symbols are ignored when using Jason dot string of phi. 93 00:07:18,020 --> 00:07:18,350 All right. 94 00:07:18,350 --> 00:07:24,830 Now Jason does string of what it does is it takes javascript object literal and turns it into adjacent 95 00:07:24,830 --> 00:07:25,750 string. 96 00:07:25,760 --> 00:07:27,260 So let me give you an example. 97 00:07:27,260 --> 00:07:36,200 First of all I'm going to put a comment here that says symbols are ignored by Jason Dodd stratified 98 00:07:36,200 --> 00:07:48,110 so say Konsole dog log and let's say Jason Daut string of phi and go ahead and put a regular object 99 00:07:48,110 --> 00:07:53,130 in here we'll just say the set to the string of Propp. 100 00:07:53,150 --> 00:08:01,420 So if we save that you're going to comment that you'll see that it logs it as a Giese in a string. 101 00:08:01,610 --> 00:08:01,940 All right. 102 00:08:01,940 --> 00:08:08,350 Now if we were to do the same thing here using a symbol as a key. 103 00:08:08,720 --> 00:08:17,570 So let's get rid of that and we'll just go ahead and put in brackets and say symbol say symbol and we'll 104 00:08:17,570 --> 00:08:24,960 give it an idea of some one and we'll go ahead and save and you'll see that it's just an empty object. 105 00:08:24,980 --> 00:08:27,610 OK so it doesn't actually. 106 00:08:27,620 --> 00:08:31,090 It doesn't actually parse as as this one did. 107 00:08:31,470 --> 00:08:37,430 OK so just some things that are just different when you're using symbols. 108 00:08:37,430 --> 00:08:37,700 All right. 109 00:08:37,700 --> 00:08:41,600 So I think that's going to do it for now for symbols in the next video. 110 00:08:41,600 --> 00:08:45,680 What I want to do is talk about error handling We haven't really got into that yet. 111 00:08:45,680 --> 00:08:50,420 I want to talk about try catch blocks and how to throw errors things like that. 112 00:08:50,420 --> 00:08:52,560 All right so I will see you in the next lecture.