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These are the user uploaded subtitles that are being translated: 1 1 00:00:01,470 --> 00:00:03,190 Let's start this section 2 2 00:00:03,190 --> 00:00:06,520 by learning how numbers work in JavaScript, 3 3 00:00:06,520 --> 00:00:09,340 how to convert values to numbers 4 4 00:00:09,340 --> 00:00:13,713 and also how to check if certain values are numbers or not. 5 5 00:00:15,570 --> 00:00:17,424 And before starting this section, 6 6 00:00:17,424 --> 00:00:20,400 go ahead and open up your starter files 7 7 00:00:20,400 --> 00:00:23,680 for this section so that we can take a look here 8 8 00:00:23,680 --> 00:00:26,220 at the script.js. 9 9 00:00:26,220 --> 00:00:28,759 So as I said, in the last section, 10 10 00:00:28,759 --> 00:00:31,490 in this one, we will continue working 11 11 00:00:31,490 --> 00:00:34,532 on our Bankist application, okay? 12 12 00:00:34,532 --> 00:00:37,810 Now, what's different here 13 13 00:00:37,810 --> 00:00:40,930 is that now we have actually different data. 14 14 00:00:40,930 --> 00:00:44,793 So we have only two accounts now here 15 15 00:00:44,793 --> 00:00:48,210 and each account now has a new array, 16 16 00:00:48,210 --> 00:00:50,853 which contains the dates of the movements. 17 17 00:00:51,830 --> 00:00:53,910 We also have the currency property 18 18 00:00:53,910 --> 00:00:56,720 and a locale property. 19 19 00:00:56,720 --> 00:00:59,670 Now, right, and so we will use this data 20 20 00:00:59,670 --> 00:01:03,650 in later lectures of this section, okay? 21 21 00:01:03,650 --> 00:01:06,550 Then down here, we have the complete application 22 22 00:01:06,550 --> 00:01:08,850 that we built in the last section. 23 23 00:01:08,850 --> 00:01:10,820 And if you want, you can go ahead 24 24 00:01:10,820 --> 00:01:14,510 and replace this entire code that I have here 25 25 00:01:14,510 --> 00:01:18,300 with your own code from the last section, okay? 26 26 00:01:18,300 --> 00:01:21,560 What matters here is that we make the application work 27 27 00:01:21,560 --> 00:01:25,683 just as it was working by the end of the last section. 28 28 00:01:26,650 --> 00:01:27,780 All right? 29 29 00:01:27,780 --> 00:01:30,970 So again, we have the same application, 30 30 00:01:30,970 --> 00:01:33,700 only the starter data is a little bit different 31 31 00:01:33,700 --> 00:01:36,310 but everything else is the same. 32 32 00:01:36,310 --> 00:01:41,090 And so now let's start learning a little bit about numbers. 33 33 00:01:41,090 --> 00:01:43,680 And the first thing that you should know about numbers 34 34 00:01:43,680 --> 00:01:45,190 is that in JavaScript, 35 35 00:01:45,190 --> 00:01:47,940 all numbers are presented internally 36 36 00:01:47,940 --> 00:01:50,140 as floating point numbers. 37 37 00:01:50,140 --> 00:01:52,720 So basically, always as decimals, 38 38 00:01:52,720 --> 00:01:55,160 no matter if we actually write them 39 39 00:01:55,160 --> 00:01:59,020 as integers or as decimals. 40 40 00:01:59,020 --> 00:02:01,043 So we can show that by doing this. 41 41 00:02:03,770 --> 00:02:05,543 So we need a new terminal here. 42 42 00:02:10,640 --> 00:02:13,053 And so here is our application back again. 43 43 00:02:13,980 --> 00:02:16,763 Let's close this and open up the console. 44 44 00:02:17,940 --> 00:02:19,140 Give it some more space 45 45 00:02:20,300 --> 00:02:25,300 and so you see that 23 is, in fact, the same as 23.0. 46 46 00:02:26,010 --> 00:02:27,050 Okay? 47 47 00:02:27,050 --> 00:02:29,800 And that's the reason why we only have one data type 48 48 00:02:29,800 --> 00:02:31,560 for all numbers. 49 49 00:02:31,560 --> 00:02:34,360 Also, numbers are represented internally 50 50 00:02:34,360 --> 00:02:37,440 in a 64 base 2 format. 51 51 00:02:37,440 --> 00:02:40,230 So that means that numbers are always stored 52 52 00:02:40,230 --> 00:02:42,020 in a binary format. 53 53 00:02:42,020 --> 00:02:46,720 So basically, they're only composed of zeros and ones. 54 54 00:02:46,720 --> 00:02:48,630 Now, in this binary form, 55 55 00:02:48,630 --> 00:02:51,720 it is very hard to represent some fractions 56 56 00:02:51,720 --> 00:02:54,000 that are very easy to represent 57 57 00:02:54,000 --> 00:02:57,170 in the base 10 system that we are used to. 58 58 00:02:57,170 --> 00:03:02,120 So base 10 is basically the numbers from zero to nine, 59 59 00:03:02,120 --> 00:03:05,850 while binary is base 2 60 60 00:03:05,850 --> 00:03:10,460 and so that's the numbers zero and one. 61 61 00:03:10,460 --> 00:03:11,610 Okay? 62 62 00:03:11,610 --> 00:03:14,190 So as I was saying, there are certain numbers 63 63 00:03:14,190 --> 00:03:17,540 that are very difficult to represent in base 2. 64 64 00:03:17,540 --> 00:03:21,822 And one example of that is the fraction 0.1. 65 65 00:03:21,822 --> 00:03:26,446 And that then results in very weird results like this. 66 66 00:03:26,446 --> 00:03:29,550 And this is kind of a classic 67 67 00:03:29,550 --> 00:03:32,210 or a running joke in JavaScript 68 68 00:03:32,210 --> 00:03:35,177 because this result should, of course, be 0.3 69 69 00:03:36,150 --> 00:03:38,740 and not with all of these zeros here. 70 70 00:03:38,740 --> 00:03:41,486 But JavaScript simply has no better way 71 71 00:03:41,486 --> 00:03:43,570 of representing this number. 72 72 00:03:43,570 --> 00:03:45,970 So in base 10, 73 73 00:03:45,970 --> 00:03:50,970 1/10 is simply 0.1. 74 74 00:03:52,510 --> 00:03:54,820 And so that's very easy to represent. 75 75 00:03:54,820 --> 00:03:58,013 But, for example, if we were trying to do 3/10, 76 76 00:03:59,260 --> 00:04:03,700 then that is also impossible to represent for us, right? 77 77 00:04:03,700 --> 00:04:05,700 It would be this number here 78 78 00:04:05,700 --> 00:04:08,890 and three until infinity, okay? 79 79 00:04:08,890 --> 00:04:13,600 And so in binary, the same thing happens with 0.1. 80 80 00:04:13,600 --> 00:04:15,990 So we get basically an infinite fraction 81 81 00:04:15,990 --> 00:04:19,793 and that then results in a weird result like this one. 82 82 00:04:20,670 --> 00:04:23,540 Now, in some cases, JavaScript does some rounding 83 83 00:04:23,540 --> 00:04:25,760 behind the scenes to try its best 84 84 00:04:25,760 --> 00:04:27,740 to hide these problems 85 85 00:04:27,740 --> 00:04:30,310 but some operations, such as this one, 86 86 00:04:30,310 --> 00:04:32,620 simply cannot mask the fact 87 87 00:04:32,620 --> 00:04:33,760 that behind the scenes, 88 88 00:04:33,760 --> 00:04:36,750 they cannot represent certain fractions. 89 89 00:04:36,750 --> 00:04:40,130 And by the way, many other languages use the same system. 90 90 00:04:40,130 --> 00:04:42,580 For example, PHP or Ruby 91 91 00:04:42,580 --> 00:04:45,610 and so don't let anyone make fun of JavaScript 92 92 00:04:45,610 --> 00:04:47,840 because of this, okay? 93 93 00:04:47,840 --> 00:04:50,540 So we just have to accept that it works this way 94 94 00:04:50,540 --> 00:04:53,800 because we really cannot do anything against this. 95 95 00:04:53,800 --> 00:04:54,980 So just be aware 96 96 00:04:54,980 --> 00:04:58,740 that you cannot do like really precise scientific 97 97 00:04:58,740 --> 00:05:01,480 or financial calculations in JavaScript 98 98 00:05:01,480 --> 00:05:05,692 because eventually, you will run into a problem like this. 99 99 00:05:05,692 --> 00:05:10,692 So .2, which will result in false, 100 100 00:05:11,290 --> 00:05:14,140 which, of course, is incorrect as we know. 101 101 00:05:14,140 --> 00:05:17,550 This should be true but well, this is simply an error 102 102 00:05:17,550 --> 00:05:22,117 in JavaScript that we have to accept, okay? 103 103 00:05:22,117 --> 00:05:24,320 All right, now that we know 104 104 00:05:24,320 --> 00:05:26,690 how JavaScript represents numbers, 105 105 00:05:26,690 --> 00:05:29,690 let's go back to actually working with them. 106 106 00:05:29,690 --> 00:05:34,167 So we know how to convert a string to a number, right? 107 107 00:05:34,167 --> 00:05:37,610 So that's like this. 108 108 00:05:37,610 --> 00:05:40,050 But there's also an easier way. 109 109 00:05:40,050 --> 00:05:42,420 So kind of a trick that we can use, 110 110 00:05:42,420 --> 00:05:46,950 which is to, or actually this should be a string, 111 111 00:05:46,950 --> 00:05:49,173 otherwise that doesn't make much sense. 112 112 00:05:50,090 --> 00:05:51,480 But as I was saying, 113 113 00:05:51,480 --> 00:05:52,860 there is an easier way, 114 114 00:05:52,860 --> 00:05:56,600 which is simply plus 23 the string. 115 115 00:05:56,600 --> 00:05:57,433 And this works 116 116 00:05:57,433 --> 00:06:01,020 because when JavaScript sees the plus operator, 117 117 00:06:01,020 --> 00:06:02,930 it will do type coercion. 118 118 00:06:02,930 --> 00:06:05,010 So it will automatically convert all 119 119 00:06:05,010 --> 00:06:06,910 the operands to numbers. 120 120 00:06:06,910 --> 00:06:11,550 And so therefore, we see 23 here in both these cases. 121 121 00:06:11,550 --> 00:06:14,393 So in this purple color, which are numbers. 122 122 00:06:16,470 --> 00:06:19,530 So this here makes our code look a lot cleaner 123 123 00:06:19,530 --> 00:06:20,720 in my opinion 124 124 00:06:20,720 --> 00:06:23,450 and so let's now actually go to our project 125 125 00:06:23,450 --> 00:06:26,130 and replace all the occurrences of Number, 126 126 00:06:26,130 --> 00:06:28,503 simply with the plus sign. 127 127 00:06:29,700 --> 00:06:31,043 So here. 128 128 00:06:32,780 --> 00:06:35,530 And if I save it now, the Prettier extension 129 129 00:06:35,530 --> 00:06:38,020 should get rid of the parentheses here. 130 130 00:06:38,020 --> 00:06:38,923 And it does. 131 131 00:06:41,960 --> 00:06:44,003 So here and here. 132 132 00:06:46,980 --> 00:06:48,463 And here as well. 133 133 00:06:51,940 --> 00:06:53,173 And that should be it. 134 134 00:06:54,720 --> 00:06:55,853 Yeah, that's it. 135 135 00:06:56,750 --> 00:06:57,810 Great. 136 136 00:06:57,810 --> 00:07:00,070 And so our project will work the same 137 137 00:07:00,070 --> 00:07:02,120 but the code is a little bit cleaner now. 138 138 00:07:02,990 --> 00:07:07,083 Okay, so here we converted strings to numbers. 139 139 00:07:08,700 --> 00:07:11,793 But we can also do something called parsing. 140 140 00:07:13,210 --> 00:07:15,883 So we can parse a number from a string. 141 141 00:07:17,980 --> 00:07:19,950 So on the Number object, 142 142 00:07:19,950 --> 00:07:22,140 which is kind of this function here, 143 143 00:07:22,140 --> 00:07:23,910 but it's also an object in the end. 144 144 00:07:23,910 --> 00:07:28,040 Remember because every function is also an object. 145 145 00:07:28,040 --> 00:07:29,540 And this number object here 146 146 00:07:29,540 --> 00:07:32,363 has some methods to do parsing. 147 147 00:07:33,200 --> 00:07:34,890 So let's use parseInt 148 148 00:07:37,050 --> 00:07:39,950 and so here we can now specify a string 149 149 00:07:40,800 --> 00:07:44,330 and that string can even include some symbols. 150 150 00:07:44,330 --> 00:07:46,500 And JavaScript will then automatically try 151 151 00:07:46,500 --> 00:07:48,180 to figure out the number 152 152 00:07:48,180 --> 00:07:49,860 that is in this string. 153 153 00:07:49,860 --> 00:07:50,693 All right? 154 154 00:07:50,693 --> 00:07:52,750 And so here we get 30. 155 155 00:07:52,750 --> 00:07:54,410 And this is actually a number. 156 156 00:07:54,410 --> 00:07:55,950 It's not a string. 157 157 00:07:55,950 --> 00:07:57,280 All right? 158 158 00:07:57,280 --> 00:07:58,905 Now, in order to make this work, 159 159 00:07:58,905 --> 00:08:03,140 the string needs to start with a number. 160 160 00:08:03,140 --> 00:08:05,890 So if we have something like this, 161 161 00:08:05,890 --> 00:08:06,917 then it's not gonna work 162 162 00:08:06,917 --> 00:08:09,250 and we get not a number. 163 163 00:08:09,250 --> 00:08:10,260 Okay? 164 164 00:08:10,260 --> 00:08:13,180 So this is a little bit like type coercion 165 165 00:08:13,180 --> 00:08:14,810 but even more advanced 166 166 00:08:14,810 --> 00:08:17,320 because as we just saw, 167 167 00:08:17,320 --> 00:08:20,740 it tries to get rid of unnecessary symbols 168 168 00:08:20,740 --> 00:08:22,520 that are not numbers. 169 169 00:08:22,520 --> 00:08:24,930 And this can be very useful, for example, 170 170 00:08:24,930 --> 00:08:29,230 in this situation where we get some kind of unit from CSS 171 171 00:08:29,230 --> 00:08:32,710 and then need to get rid of that unit. 172 172 00:08:32,710 --> 00:08:33,909 Now, the parseInt function 173 173 00:08:33,909 --> 00:08:37,090 actually accepts a second argument, 174 174 00:08:37,090 --> 00:08:39,570 which is the so-called regex. 175 175 00:08:39,570 --> 00:08:42,530 And the regex is the base of the numeral system 176 176 00:08:42,530 --> 00:08:44,150 that we are using. 177 177 00:08:44,150 --> 00:08:47,460 So here we are simply using base 10 numbers. 178 178 00:08:47,460 --> 00:08:50,140 So numbers from zero to nine. 179 179 00:08:50,140 --> 00:08:52,890 And most of the time, we are doing that 180 180 00:08:52,890 --> 00:08:55,773 and so we should always pass in the number 10 here. 181 181 00:08:57,660 --> 00:09:01,970 Okay, so that can avoid some bugs in some situations. 182 182 00:09:01,970 --> 00:09:04,500 And you see the result here is the same. 183 183 00:09:04,500 --> 00:09:07,450 But if we were working, for example, with binary, 184 184 00:09:07,450 --> 00:09:09,840 then we would write two 185 185 00:09:09,840 --> 00:09:12,963 and then the result would be completely different. 186 186 00:09:14,090 --> 00:09:16,610 In this case, we cannot even see it. 187 187 00:09:16,610 --> 00:09:19,000 But let's just keep using 10 here. 188 188 00:09:19,000 --> 00:09:22,260 So this is with integers. 189 189 00:09:22,260 --> 00:09:24,660 So that's what the int here stands for. 190 190 00:09:24,660 --> 00:09:29,294 So parse integers but there's also parseFloat. 191 191 00:09:29,294 --> 00:09:34,294 So Number.parseFloat 192 192 00:09:35,730 --> 00:09:38,193 and let's now try 2.5rem. 193 193 00:09:41,830 --> 00:09:44,940 And so now it reads the decimal number here 194 194 00:09:44,940 --> 00:09:46,420 from our string. 195 195 00:09:46,420 --> 00:09:48,760 So a floating point number. 196 196 00:09:48,760 --> 00:09:52,053 Let's see what happens if we used Int. 197 197 00:09:53,230 --> 00:09:57,340 And then we only get the integer part, right? 198 198 00:09:57,340 --> 00:10:00,970 So it will then stop here at this decimal point 199 199 00:10:00,970 --> 00:10:03,660 but that, of course, not what we want. 200 200 00:10:03,660 --> 00:10:04,493 And by the way, 201 201 00:10:04,493 --> 00:10:08,160 we could even have like some white space down here 202 202 00:10:08,160 --> 00:10:11,383 that would not affect anything at all. 203 203 00:10:12,694 --> 00:10:14,060 All right? 204 204 00:10:14,060 --> 00:10:17,060 Now, by the way, these two functions here 205 205 00:10:17,060 --> 00:10:20,483 are actually also so-called global functions. 206 206 00:10:22,090 --> 00:10:24,833 So we would not have to call them on Number. 207 207 00:10:26,570 --> 00:10:28,383 So this here also works. 208 208 00:10:29,380 --> 00:10:31,890 Okay, but this is the more traditional 209 209 00:10:31,890 --> 00:10:34,150 and old-school way of doing it. 210 210 00:10:34,150 --> 00:10:35,590 Now in modern JavaScript, 211 211 00:10:35,590 --> 00:10:38,860 it is more encouraged to call these functions 212 212 00:10:38,860 --> 00:10:42,320 actually on the Number object, okay? 213 213 00:10:42,320 --> 00:10:46,010 So we say that Number here provides something 214 214 00:10:46,010 --> 00:10:48,530 called a namespace, all right? 215 215 00:10:48,530 --> 00:10:51,560 So a namespace for all these different functions, 216 216 00:10:51,560 --> 00:10:54,213 like parseFloat, and parseInt. 217 217 00:10:55,470 --> 00:10:58,900 But anyway, let's now explore another function 218 218 00:10:58,900 --> 00:11:01,310 of the Number namespace 219 219 00:11:01,310 --> 00:11:04,070 and that is the isNaN. 220 220 00:11:04,070 --> 00:11:05,573 So is not a number. 221 221 00:11:08,010 --> 00:11:09,583 So Number.IsNotaNumber. 222 222 00:11:11,740 --> 00:11:13,270 And we can use this one 223 223 00:11:13,270 --> 00:11:16,880 to basically check if any value is a number. 224 224 00:11:16,880 --> 00:11:20,750 Well, not any value but more about that later. 225 225 00:11:20,750 --> 00:11:23,570 So for example, if we pass 20, 226 226 00:11:23,570 --> 00:11:26,830 then here we got false. 227 227 00:11:26,830 --> 00:11:28,610 And so is it not a number? 228 228 00:11:28,610 --> 00:11:30,890 False, all right? 229 229 00:11:30,890 --> 00:11:33,133 So let's try the same with a string. 230 230 00:11:34,540 --> 00:11:35,373 20. 231 231 00:11:36,300 --> 00:11:39,510 And so here we also get false, all right? 232 232 00:11:39,510 --> 00:11:42,330 Because this also isn't not a number. 233 233 00:11:42,330 --> 00:11:46,160 It's just a regular value, right? 234 234 00:11:46,160 --> 00:11:49,454 But now let's try it by converting something. 235 235 00:11:49,454 --> 00:11:51,920 So for example, this string, 236 236 00:11:51,920 --> 00:11:54,490 if we try to convert it to a number, 237 237 00:11:54,490 --> 00:11:56,403 then this will be not a number. 238 238 00:11:57,900 --> 00:11:58,733 Right? 239 239 00:11:58,733 --> 00:12:00,293 And so therefore, it is true. 240 240 00:12:01,460 --> 00:12:03,173 So let's just do that here. 241 241 00:12:04,580 --> 00:12:06,283 So yeah, this works as well. 242 242 00:12:07,200 --> 00:12:10,440 And so you see this is, of course, not a number. 243 243 00:12:10,440 --> 00:12:11,750 All right? 244 244 00:12:11,750 --> 00:12:13,653 But let's try something else. 245 245 00:12:15,210 --> 00:12:20,070 Let's, for example, divide 23 by zero 246 246 00:12:20,070 --> 00:12:22,910 and maybe you know that dividing by zero 247 247 00:12:22,910 --> 00:12:25,900 gives us infinite, okay? 248 248 00:12:25,900 --> 00:12:27,810 So dividing by zero is something 249 249 00:12:27,810 --> 00:12:30,180 that's not allowed in mathematics 250 250 00:12:30,180 --> 00:12:33,070 and so it will give us infinity. 251 251 00:12:33,070 --> 00:12:36,600 So infinity is also not not a NaN 252 252 00:12:37,450 --> 00:12:40,223 and so therefore, we get false here as well. 253 253 00:12:41,070 --> 00:12:43,383 So let me just demonstrate that here. 254 254 00:12:44,910 --> 00:12:49,200 So indeed, this gives us this special value of infinity 255 255 00:12:49,200 --> 00:12:52,220 that also exists in JavaScript. 256 256 00:12:52,220 --> 00:12:55,510 And so this is not a number 257 257 00:12:55,510 --> 00:12:57,380 is actually not a perfect way 258 258 00:12:57,380 --> 00:12:59,880 for checking if a value is a number 259 259 00:12:59,880 --> 00:13:03,050 because it doesn't consider this use case 260 260 00:13:03,050 --> 00:13:05,660 and sometimes, this might very well happen. 261 261 00:13:05,660 --> 00:13:09,013 And therefore, there is a better method called isFinite. 262 262 00:13:11,730 --> 00:13:15,800 So Number.isFinite and let's try it 263 263 00:13:15,800 --> 00:13:17,108 with the same numbers. 264 264 00:13:17,108 --> 00:13:19,343 So here we get true. 265 265 00:13:21,060 --> 00:13:24,610 And okay, and so basically this should be the opposite now 266 266 00:13:24,610 --> 00:13:26,090 of this one 267 267 00:13:26,090 --> 00:13:28,800 because this is not not a number. 268 268 00:13:28,800 --> 00:13:30,133 But it is finite. 269 269 00:13:31,300 --> 00:13:32,438 Okay? 270 270 00:13:32,438 --> 00:13:34,593 Now, if you try it with 20, 271 271 00:13:35,740 --> 00:13:39,200 the string, then here we get false 272 272 00:13:39,200 --> 00:13:41,340 because it's not a number. 273 273 00:13:41,340 --> 00:13:43,210 And so this is actually better to check 274 274 00:13:43,210 --> 00:13:45,543 if something is a number or not. 275 275 00:13:47,000 --> 00:13:49,600 And I know this sounds a bit confusing, 276 276 00:13:49,600 --> 00:13:51,511 and the confusion comes from the fact 277 277 00:13:51,511 --> 00:13:53,820 that we have this weird thing here 278 278 00:13:53,820 --> 00:13:56,383 that is also called not a number. 279 279 00:13:57,250 --> 00:13:58,400 All right? 280 280 00:13:58,400 --> 00:14:00,700 And so therefore, I'm just telling you 281 281 00:14:00,700 --> 00:14:04,350 that the isFinite method is indeed the best way 282 282 00:14:04,350 --> 00:14:07,803 of checking if a value is a number. 283 283 00:14:10,640 --> 00:14:13,463 So a real number, not a string. 284 284 00:14:15,320 --> 00:14:16,820 All right? 285 285 00:14:16,820 --> 00:14:18,893 So let's try again this one here. 286 286 00:14:20,440 --> 00:14:21,760 Trying to convert it 287 287 00:14:21,760 --> 00:14:24,670 and we know that this here is not a number. 288 288 00:14:24,670 --> 00:14:27,843 So literally, this will be NaN. 289 289 00:14:28,730 --> 00:14:29,650 Right? 290 290 00:14:29,650 --> 00:14:31,913 And so this should be false as well. 291 291 00:14:33,130 --> 00:14:34,600 And it is. 292 292 00:14:34,600 --> 00:14:36,683 And now finally, this last use case, 293 293 00:14:37,950 --> 00:14:39,623 which gives us infinity. 294 294 00:14:42,060 --> 00:14:44,780 And so it is false as well. 295 295 00:14:44,780 --> 00:14:46,970 So that's where the name of the method 296 296 00:14:46,970 --> 00:14:48,300 actually comes from. 297 297 00:14:48,300 --> 00:14:52,663 So isFinite and so infinity is, of course, not finite. 298 298 00:14:54,110 --> 00:14:55,070 All right? 299 299 00:14:55,070 --> 00:14:57,470 And so this method is the ultimate method 300 300 00:14:57,470 --> 00:15:01,500 that you should use to check if any value is a number, 301 301 00:15:01,500 --> 00:15:04,960 at least when you're working with floating point numbers. 302 302 00:15:04,960 --> 00:15:06,300 So if you are sure 303 303 00:15:06,300 --> 00:15:08,860 that you just need to check for an integer, 304 304 00:15:08,860 --> 00:15:11,113 then you can use isInteger as well. 305 305 00:15:12,598 --> 00:15:16,393 So let me just write here a comment as well. 306 306 00:15:17,540 --> 00:15:19,130 So this one you should only use 307 307 00:15:19,130 --> 00:15:24,130 to check if value is not a number. 308 308 00:15:24,250 --> 00:15:27,934 So literally, not a number this value. 309 309 00:15:27,934 --> 00:15:28,913 Okay? 310 310 00:15:31,070 --> 00:15:32,800 But usually, in practice, 311 311 00:15:32,800 --> 00:15:34,520 I never use this. 312 312 00:15:34,520 --> 00:15:36,660 Whenever I need to check for a number, 313 313 00:15:36,660 --> 00:15:38,440 this is the one to go 314 314 00:15:38,440 --> 00:15:40,820 or if I'm using integers, 315 315 00:15:40,820 --> 00:15:45,273 then I use isInteger as I was just saying before. 316 316 00:15:46,440 --> 00:15:47,893 So we can do this. 317 317 00:15:49,560 --> 00:15:53,470 Also this is also an integer remember 318 318 00:15:53,470 --> 00:15:56,930 and so both are true, okay? 319 319 00:15:56,930 --> 00:16:00,910 But then, of course, if we try this here, 320 320 00:16:00,910 --> 00:16:02,940 it will be false. 321 321 00:16:02,940 --> 00:16:05,550 Now, in our project that we're currently building, 322 322 00:16:05,550 --> 00:16:07,970 there's not really a need to check 323 323 00:16:07,970 --> 00:16:11,260 if any of the inputs is really a number or not 324 324 00:16:11,260 --> 00:16:13,260 and so in this particular case, 325 325 00:16:13,260 --> 00:16:15,730 we don't need to go back and change anything 326 326 00:16:15,730 --> 00:16:17,970 but it's still good to know about, 327 327 00:16:17,970 --> 00:16:20,150 especially this method here. 328 328 00:16:20,150 --> 00:16:21,600 So this is your go-to 329 329 00:16:21,600 --> 00:16:23,010 whenever you need to check 330 330 00:16:23,010 --> 00:16:25,818 if something is a number or not. 331 331 00:16:25,818 --> 00:16:28,270 And going back here, 332 332 00:16:28,270 --> 00:16:30,750 the parseFloat function should be your go-to 333 333 00:16:30,750 --> 00:16:34,284 whenever you need to read a value out of a string. 334 334 00:16:34,284 --> 00:16:37,078 For example, coming from CSS. 335 335 00:16:37,078 --> 00:16:39,010 So then you always get this 336 336 00:16:39,010 --> 00:16:40,330 and it's very nice to be able 337 337 00:16:40,330 --> 00:16:43,023 to read the number out of the string. 27637