WEBVTT 00:01.940 --> 00:08.090 Because of that, JavaScript is a dynamically typed language, the type is associated with runtime values 00:08.330 --> 00:09.740 and not named variables. 00:10.100 --> 00:15.560 Therefore the programmer can write quicker because we do not have to specify types every time. 00:16.400 --> 00:20.540 It's nice feature, but it may sometimes cause unexpected bugs and errors. 00:21.230 --> 00:24.050 And it happens especially when we deal with type coersion. 00:25.460 --> 00:31.120 Type corrosion means that a value from one type can be converted to another on the fly. 00:32.520 --> 00:36.120 Let's see what it exactly means, create variable A. 00:37.630 --> 00:39.730 Which equals to ten plus five. 00:41.340 --> 00:42.690 And run it in council. 00:46.900 --> 00:51.740 It's definitely 15 and type of the result value is a number. 00:51.790 --> 00:56.770 You see the color of it is blue now put five within quotes. 00:57.730 --> 01:00.910 And make it strong, so what do you expect to get? 01:01.450 --> 01:10.210 We have no number 10 and on the other hand, we have five, which is I think, let's see, we have one 01:10.210 --> 01:11.770 zero five in council. 01:12.910 --> 01:14.860 So let me explain what has happened here. 01:14.950 --> 01:18.130 JavaScript engine has found plus sign in the statement. 01:18.670 --> 01:25.810 And you know, that plus sign belongs to Earth magical operators, but simultaneously it works for string 01:25.810 --> 01:26.290 values. 01:26.830 --> 01:34.240 It concatenate them, for example, we can concatenate multiple string values like this, create another 01:34.240 --> 01:35.560 variable be. 01:36.850 --> 01:38.440 Which equals to hello. 01:40.300 --> 01:41.740 Done plus, dear. 01:44.580 --> 01:45.810 Plus, student. 01:48.290 --> 01:50.630 And run this variable in council. 01:55.600 --> 01:59.800 So you can see hello to your students, which is a string value. 02:00.970 --> 02:06.970 All right, let's go back to the first example in which JavaScript engine has to decide either convert 02:07.570 --> 02:09.400 to string or five to number. 02:10.330 --> 02:17.230 The people who has created this nice programming language decided that in this case, it should be converted 02:17.230 --> 02:18.550 to a string value. 02:19.090 --> 02:22.210 And this whole process is called type conversion. 02:22.390 --> 02:25.270 JavaScript engine has course turned to a string. 02:25.840 --> 02:31.840 But the key point is that we did not ask for doing that to the engine when JavaScript engine. 02:31.880 --> 02:36.160 So this statement is automatically coerced number into three. 02:37.040 --> 02:44.950 Okay, let's see what happens if we use other arithmetical operator, let's say multiplication and you 02:44.950 --> 02:52.120 see that we have 50, if we look at this number, will find that it has blue color because it's actually 02:52.120 --> 02:52.510 no. 02:53.140 --> 03:00.370 So JavaScript engine has caused five into number because multiplication is an arithmetical operator 03:00.370 --> 03:02.170 and it's used with numbers only. 03:03.680 --> 03:13.730 All right, let's consider another case, right, verbal a equals two, five plus ten plus the. 03:15.750 --> 03:19.140 Which is string and luggage in council. 03:22.130 --> 03:26.020 You see that we have got to be OK. 03:27.320 --> 03:35.870 Now, let's place B before 5:00, right, verbal sequels to be plus five, plus 10. 03:38.580 --> 03:40.470 And Reinertsen Castle. 03:44.620 --> 03:48.130 So we have now be five, 10. 03:49.230 --> 03:53.250 We have got different results in both cases, and it seems to be right. 03:53.970 --> 03:55.170 Let's explain what happened. 03:55.650 --> 03:59.830 As you already know, JavaScript engine with the codes from left to right. 04:00.270 --> 04:06.750 So in the first case, it has found numbers for the first operation and has added them as the numbers. 04:07.440 --> 04:12.090 So the value became 15 and after that it has caused it to shrink. 04:12.480 --> 04:17.610 And we have got 15 P as for the second case engine. 04:17.640 --> 04:23.000 So the string at the beginning of the value and then it has caused five to eight Twigg. 04:23.790 --> 04:30.690 So we got B five after the first operation and in the same way it has caused 10 to string. 04:31.230 --> 04:34.440 Therefore we got the string value B five 10. 04:36.220 --> 04:36.910 Makes sense. 04:38.440 --> 04:45.040 All right, remember that all of these things happen on the right time, on the fly time, caution is 04:45.040 --> 04:47.590 very odd process, so you should understand it. 04:47.590 --> 04:53.640 Well, type caution also accused with comparison operators, which you are already familiar with. 04:54.280 --> 04:58.690 Let's write in console five, triple EcoStar five. 04:59.410 --> 05:02.020 It's true and there is nothing surprising here. 05:02.830 --> 05:08.020 Now writes five triple equals to five and triple equals to five. 05:08.980 --> 05:12.540 From human perspective, you may expect your true as well. 05:13.420 --> 05:14.050 Let's see. 05:14.320 --> 05:15.600 And we have false. 05:16.630 --> 05:18.190 Let's figure out what has happened. 05:18.940 --> 05:23.890 Five triple equals five is definitely true and true as boolean value. 05:24.520 --> 05:27.310 So we have got to after first triple equals. 05:27.880 --> 05:31.680 Therefore the next triple equals has compared the boolean value. 05:31.690 --> 05:32.110 True. 05:32.500 --> 05:36.190 And the number five and therefore it became false. 05:37.690 --> 05:38.370 Makes sense. 05:40.270 --> 05:47.920 OK, actually, this is what happened on the fly through triple the cost of five, generally, balloon 05:47.920 --> 05:49.710 values can be caught into numbers. 05:49.720 --> 05:55.570 I mean, that true can be coerced into one and falls into zero to prove that. 05:56.560 --> 05:57.330 That's right. 05:57.340 --> 05:59.410 True double equals to one. 06:01.000 --> 06:07.450 Double equal Equilar Compass, as we remember, only values and not data types, so here we have two. 06:08.050 --> 06:09.790 The same happens with false. 06:10.270 --> 06:14.980 If we write false double equals zero, then we will get through. 06:17.140 --> 06:24.880 But in case of triple equals, we will have opposite values, so as I already recommended, in order 06:24.880 --> 06:32.230 to avoid unexpected results which may cause errors in bugs that then are hard to find and debug, the 06:32.230 --> 06:37.270 solution is to use triple EQUASS operator because it's always a better practice. 06:38.980 --> 06:44.650 OK, if you are new in programming, you may be a little bit confused and you may think where you can 06:44.650 --> 06:46.060 use those little details. 06:46.480 --> 06:52.020 But trust me, when you work with tons of lines of code in the future, it will definitely help you. 06:53.560 --> 06:54.040 All right. 06:54.670 --> 07:00.370 And just like we have discussed what type corrosion is, how it works with comparison operators, and 07:00.370 --> 07:02.530 we have seen some interesting and weird things. 07:03.460 --> 07:04.830 OK, let's move on.