1 00:00:01,160 --> 00:00:04,130 Starting from year's 2021. 2 00:00:04,130 --> 00:00:07,600 We can use a feature called "Numeric Separators" 3 00:00:07,600 --> 00:00:09,850 to format numbers in a way 4 00:00:09,850 --> 00:00:11,550 that is easier for us, 5 00:00:11,550 --> 00:00:15,393 or for other developers to read and to understand. 6 00:00:16,980 --> 00:00:18,850 Let's say that we wanted to represent 7 00:00:18,850 --> 00:00:20,760 a really large number. 8 00:00:20,760 --> 00:00:24,113 For example, the diameter of our solar system. 9 00:00:25,320 --> 00:00:27,670 Let's say a diameter, 10 00:00:27,670 --> 00:00:32,670 which is 287,460,000,000. 11 00:00:34,070 --> 00:00:36,640 And just from looking at this number here, 12 00:00:36,640 --> 00:00:41,050 it's really difficult to read and to understand it. 13 00:00:41,050 --> 00:00:45,730 Does this mean like 28 billion or is it just 2 billion 14 00:00:45,730 --> 00:00:48,090 or really what is this number? 15 00:00:48,090 --> 00:00:50,120 It's really hard to read like this. 16 00:00:50,120 --> 00:00:52,363 There is just too many zeros here. 17 00:00:53,970 --> 00:00:55,660 Now to help with this, 18 00:00:55,660 --> 00:00:58,210 when we write a number this large 19 00:00:58,210 --> 00:01:00,010 under normal English language, 20 00:01:00,010 --> 00:01:03,713 we usually use a thousand separator like the comma. 21 00:01:04,650 --> 00:01:07,533 We would write this number like this. 22 00:01:08,640 --> 00:01:10,340 And then it becomes really easy 23 00:01:10,340 --> 00:01:14,993 to immediately see that this means 287,460,000,000. 24 00:01:16,980 --> 00:01:18,440 And now, fortunately, 25 00:01:18,440 --> 00:01:21,380 we can do the same thing in JavaScript as well, 26 00:01:21,380 --> 00:01:23,910 using the new numeric separators. 27 00:01:25,090 --> 00:01:27,930 Numeric separators are simply underscores 28 00:01:27,930 --> 00:01:30,610 that we can place anywhere that we want in 29 00:01:30,610 --> 00:01:32,010 or numbers, 30 00:01:32,010 --> 00:01:36,000 and which will make it really easy to understand 31 00:01:36,000 --> 00:01:38,493 and to parse numbers this large. 32 00:01:39,670 --> 00:01:42,820 Using the underscore here as a thousand separator, 33 00:01:42,820 --> 00:01:44,800 then makes it really easy to understand, 34 00:01:44,800 --> 00:01:45,970 that this number here 35 00:01:45,970 --> 00:01:48,883 means in fact, 287 billion. 36 00:01:51,680 --> 00:01:54,040 Now let's just log it to the console 37 00:01:54,040 --> 00:01:56,433 to see what JavaScript actually sees. 38 00:01:57,460 --> 00:01:59,680 And so here we see that in fact, 39 00:01:59,680 --> 00:02:03,140 the engine basically ignores these underscores. 40 00:02:03,140 --> 00:02:05,210 So these numeric separators. 41 00:02:05,210 --> 00:02:08,040 It simply sees the number itself. 42 00:02:08,040 --> 00:02:09,560 And so what this means, 43 00:02:09,560 --> 00:02:12,063 is that we can actually place the underscores, 44 00:02:12,900 --> 00:02:15,663 the numeric separators, anywhere that we want. 45 00:02:17,860 --> 00:02:19,950 Let's do another example. 46 00:02:19,950 --> 00:02:24,480 Let's call this one price in cents, 47 00:02:24,480 --> 00:02:26,030 and I'm gonna set it to 345_99. 48 00:02:31,170 --> 00:02:33,240 Again, using the underscore here, 49 00:02:33,240 --> 00:02:34,740 then makes it really obvious 50 00:02:34,740 --> 00:02:37,843 that this is actually a price in cents. 51 00:02:39,990 --> 00:02:43,160 Of course the number itself, does again, 52 00:02:43,160 --> 00:02:45,590 not contain the underscore. 53 00:02:45,590 --> 00:02:49,827 And our price is indeed 35,599 cents. 54 00:02:51,470 --> 00:02:53,490 But by placing the underscore here, 55 00:02:53,490 --> 00:02:55,070 it makes it really obvious, 56 00:02:55,070 --> 00:02:57,510 that we have first this value here 57 00:02:57,510 --> 00:03:00,770 and then this other value here in cents. 58 00:03:00,770 --> 00:03:04,690 And in fact, it's so obvious that we could even get rid 59 00:03:04,690 --> 00:03:08,093 of the cents part here in a variable name. 60 00:03:11,400 --> 00:03:13,770 Basically we can use the underscore now 61 00:03:13,770 --> 00:03:18,123 to give meanings to certain parts of our numbers. 62 00:03:18,123 --> 00:03:20,200 Here we said, these are thousands, 63 00:03:20,200 --> 00:03:22,483 and here we said that these are a cents. 64 00:03:25,300 --> 00:03:27,100 Lets try another one. 65 00:03:27,100 --> 00:03:30,373 Lets call this transfer fee. 66 00:03:32,810 --> 00:03:37,010 And here again, we placed the underscore like this. 67 00:03:37,010 --> 00:03:38,010 And so here immediately, 68 00:03:38,010 --> 00:03:43,010 it looks like it is $15 for example and 0 cents. 69 00:03:43,340 --> 00:03:45,703 But if we did the same thing like this, 70 00:03:48,060 --> 00:03:50,000 so placing to underscore here, 71 00:03:50,000 --> 00:03:53,633 then it suddenly looks like 1_500. 72 00:03:55,140 --> 00:03:58,590 While in fact it is the exact same number. 73 00:03:58,590 --> 00:04:01,140 Both of them are exactly 1,500. 74 00:04:01,140 --> 00:04:02,980 But just the underscore alone, 75 00:04:02,980 --> 00:04:04,500 gives them different meanings. 76 00:04:04,500 --> 00:04:06,680 And so we can use that to our advantage, 77 00:04:06,680 --> 00:04:09,833 whenever we write numbers in or JavaScript code. 78 00:04:13,250 --> 00:04:18,250 Another variable here, called PI. 79 00:04:18,300 --> 00:04:20,560 And this one is to show you some restrictions 80 00:04:20,560 --> 00:04:22,733 as to where we can place the underscore. 81 00:04:24,620 --> 00:04:26,103 PI is, 82 00:04:26,103 --> 00:04:29,110 3.1415, 83 00:04:29,110 --> 00:04:32,993 and we can only place underscores between numbers. 84 00:04:33,840 --> 00:04:35,490 We could place it here, 85 00:04:35,490 --> 00:04:37,373 and there would be no problem at all. 86 00:04:38,760 --> 00:04:39,853 Lets just log it, 87 00:04:41,640 --> 00:04:43,060 but actually to underscore 88 00:04:43,060 --> 00:04:45,450 doesn't make a lot of sense here. 89 00:04:45,450 --> 00:04:48,453 Lets remove it and let's say we wanted to place it here. 90 00:04:50,270 --> 00:04:51,680 Here we get to an error, 91 00:04:51,680 --> 00:04:53,383 because that is not allowed. 92 00:04:55,270 --> 00:04:57,840 It's also not allowed to place here, 93 00:04:57,840 --> 00:05:01,923 and also not at the beginning of a number or at the end. 94 00:05:02,820 --> 00:05:05,210 All of these are illegal, 95 00:05:05,210 --> 00:05:08,950 and like this it works, 96 00:05:08,950 --> 00:05:11,423 but we can also not place two in a row. 97 00:05:12,650 --> 00:05:15,343 The error message here is pretty explicit about that. 98 00:05:18,400 --> 00:05:21,930 And now just one final detail that we need to be aware of 99 00:05:21,930 --> 00:05:24,870 is that when we try to convert strings, 100 00:05:24,870 --> 00:05:26,430 that contain underscores, 101 00:05:26,430 --> 00:05:29,873 to a number that will not work as expected. 102 00:05:32,010 --> 00:05:34,960 Lets try to use the number of function 103 00:05:34,960 --> 00:05:38,173 that we learned before to convert a number. 104 00:05:40,260 --> 00:05:43,423 Of course with this, it should work just fine, 105 00:05:45,199 --> 00:05:50,060 We have 230,000 to the number or actually the string 106 00:05:50,060 --> 00:05:51,960 and then here it converts to a number. 107 00:05:53,230 --> 00:05:56,250 However, if we place an underscore here, 108 00:05:56,250 --> 00:05:59,430 so if we want to have a numeric separator here, 109 00:05:59,430 --> 00:06:01,370 that would not work. 110 00:06:01,370 --> 00:06:02,713 Now it is not a number. 111 00:06:04,150 --> 00:06:04,983 What that means, 112 00:06:04,983 --> 00:06:06,840 is that you should really only use, 113 00:06:06,840 --> 00:06:08,380 these numeric separators, 114 00:06:08,380 --> 00:06:11,330 when you are writing down numbers like this. 115 00:06:11,330 --> 00:06:12,780 Really in the code. 116 00:06:12,780 --> 00:06:15,330 If you need to store a number in a string, 117 00:06:15,330 --> 00:06:17,300 for example, in an API, 118 00:06:17,300 --> 00:06:20,630 or if you get a number as a string from an API, 119 00:06:20,630 --> 00:06:23,410 you should not use underscores in there, 120 00:06:23,410 --> 00:06:25,800 because then JavaScript will not be able 121 00:06:25,800 --> 00:06:29,220 to parse the number correctly out of that string. 122 00:06:29,220 --> 00:06:31,210 It's not gonna work as expected 123 00:06:31,210 --> 00:06:33,570 and you will get it's not a number, 124 00:06:33,570 --> 00:06:36,723 that might then introduce bugs into your application. 125 00:06:37,560 --> 00:06:40,907 And the same is true with the "parseInt" function. 126 00:06:44,220 --> 00:06:46,320 Here we do not get not a number, 127 00:06:46,320 --> 00:06:49,350 but we only get to 230. 128 00:06:49,350 --> 00:06:53,250 Only the parts that is here in front of the underscore. 129 00:06:53,250 --> 00:06:55,100 Everything else will then be ignored.