WEBVTT 00:01.850 --> 00:05.610 Sometimes we need to make correct decision out of several conditions. 00:05.990 --> 00:11.810 This is the case when we need to use an advanced form of Ethan's statement, and it's called if Alcivar 00:11.810 --> 00:12.320 statement. 00:13.240 --> 00:14.960 There is nothing special about this code. 00:14.980 --> 00:21.460 It's just a series of if statements to code, an elusive conditional you call the keywords Al Swift, 00:21.940 --> 00:26.710 followed by a condition in parentheses and a block of code inside Colibri. 00:27.670 --> 00:33.730 If the condition is true, it's block of code will be executed and any remaining codes in the statement 00:33.730 --> 00:34.720 will be skipped over. 00:35.020 --> 00:40.210 This will continue until one of the elusive conditions is true or they all are false. 00:41.370 --> 00:47.610 You can write multiple Elsom statements as much as you want, but LTH should be definitely only one. 00:48.540 --> 00:53.760 So, again, if this condition is true, then the block of code inside the collaborators prices will 00:53.760 --> 00:57.060 be run and all the other statements will be kept. 00:58.390 --> 01:07.430 All right, let's create variable call it prof as a profession and assign to its Disvalue instructor. 01:08.230 --> 01:12.150 Imagine that we want to get the relevant descriptions for the multiple professions. 01:12.820 --> 01:15.370 For that, we need to use several conditions. 01:15.730 --> 01:16.330 But if. 01:17.180 --> 01:20.510 Profession triple equal to instructor. 01:22.660 --> 01:23.080 Then. 01:24.160 --> 01:25.150 Run in Castle. 01:26.770 --> 01:27.790 Profession plus. 01:29.260 --> 01:30.790 Teaches students. 01:34.040 --> 01:40.940 Danus, Alsup statement with a condition if profession triple equals to Dr.. 01:43.970 --> 01:44.360 Then. 01:46.130 --> 01:48.080 Right, canceled look profession. 01:49.530 --> 01:51.630 Plus treats people. 01:54.400 --> 02:02.260 Then again, use another elusive statement with a condition if professional triple equals to composer. 02:05.380 --> 02:10.990 And run again in Castle Profession plus creates the music. 02:14.970 --> 02:18.390 And finally, right el statement. 02:20.380 --> 02:22.600 And running kosal professions. 02:24.240 --> 02:25.170 Do not match. 02:27.260 --> 02:35.150 All right, let's run this code so we have instructor teaching students that's because first condition 02:35.150 --> 02:35.630 is true. 02:36.990 --> 02:40.920 Now change the value of instructor into Dr.. 02:43.040 --> 02:50.900 Then reload the page and we have a through its people, the result is the same in this case, first 02:50.900 --> 02:54.120 elusive condition is true and that's why we have got this results. 02:55.100 --> 02:57.800 Let's change the condition in second statement. 02:57.800 --> 03:01.560 And instead of composer, write the same value. 03:01.700 --> 03:06.160 Doctor, you said that the both conditions in Alcivar statements are true. 03:06.860 --> 03:09.320 You may expect to get both results in council. 03:10.070 --> 03:11.030 Let's see what happens. 03:11.930 --> 03:15.040 Still, we have the results from the first out of statement. 03:15.620 --> 03:19.910 That's because, as we already said, one of the engine finds true condition. 03:20.480 --> 03:23.740 Then it terminates executing of the remaining statements. 03:24.920 --> 03:25.400 All right. 03:25.940 --> 03:33.830 Now change once again the value of profession into, let's say, engineer reloader page. 03:34.840 --> 03:37.120 And you see that professions do not match. 03:37.660 --> 03:43.900 It means that all the conditions are false and also statement is executed, as we said. 03:44.260 --> 03:46.660 Remember that we can use it all at once. 03:48.150 --> 03:54.000 All right, in order to check multiple conditions simultaneously in JavaScript, we can use another 03:54.000 --> 03:56.880 type of apparatus which is called logical. 03:57.510 --> 04:01.600 Logical operators are used to determine the logic between variables or values. 04:02.340 --> 04:09.990 We have three types of logical operators, logical and which is expressed with two ampersands logical 04:09.990 --> 04:16.530 or which is written by double vertical bars and logical not, which is an exclamation mark. 04:17.460 --> 04:24.750 Let's consider how each of these operators work for demonstrating that I'm going to use eval statements 04:25.350 --> 04:29.750 as we set the logical operators, allow us to compare multiple conditions. 04:30.300 --> 04:36.720 So when we use an operator with two conditions, then both of them have to be true in order to be the 04:36.720 --> 04:46.500 whole expression to write if that five triple equal to five user and operator. 04:47.370 --> 04:50.400 And then the second condition for. 04:51.540 --> 04:52.680 Triple EcoStar for. 04:54.320 --> 04:57.620 Then, if this condition is true, run in council. 04:58.580 --> 05:00.020 Condition is true. 05:04.250 --> 05:05.780 And if it's false. 05:07.230 --> 05:13.820 Then use our statement and run in causal condition is false. 05:16.590 --> 05:20.110 Reload the page and you see the condition is true. 05:20.640 --> 05:26.170 The reason is that five triple equals five is true and false report equals four is true as well. 05:26.580 --> 05:28.520 Therefore, the whole condition is true. 05:29.610 --> 05:36.060 Because of that, the component operators have higher precedence than logical operators, the engine 05:36.240 --> 05:42.600 at first compares the numbers and after that it checks if the condition is true or false for logical 05:42.600 --> 05:43.470 and operator. 05:44.800 --> 05:53.620 If we make one of the conditions false, for example, five triple equals to four, then the whole condition 05:53.620 --> 05:57.040 will be false and we will get condition is false in Castle. 05:58.030 --> 05:58.480 All right. 06:00.340 --> 06:06.310 The difference between logical and and logical are is that if one of the condition is true, that the 06:06.310 --> 06:13.060 whole condition is still true for logical or operator, so you see that the condition on the left side 06:13.060 --> 06:16.350 is false, but the condition on the right side is true. 06:16.780 --> 06:19.420 And that's why we got condition is true in Castle. 06:20.950 --> 06:28.330 Logical operator gives us false value when both conditions are false, so right for triple equals to 06:28.330 --> 06:28.700 three. 06:29.560 --> 06:33.820 Now both sides are false and therefore the whole condition is false. 06:35.420 --> 06:41.110 OK, the last logical operator not gives us always an opposite value. 06:41.590 --> 06:44.120 If the condition is true, then it returns false. 06:44.170 --> 06:51.310 So if we write here not true, we will get condition is false. 06:52.690 --> 06:59.170 All right, so let's briefly describe the logical operators that we have just discussed, logical and 06:59.170 --> 07:05.170 gives us true value when both conditions are true, if one of them or both of them are false, that 07:05.170 --> 07:06.220 it gives us false. 07:07.490 --> 07:14.870 Logical or gives us true value if both conditions are true or one of them is true, if both conditions 07:14.870 --> 07:16.910 are false, then it gives us false. 07:18.190 --> 07:25.270 As for logical not, it gives us opposite values, if the condition is true, it gives us false and 07:25.390 --> 07:26.250 vice versa. 07:28.030 --> 07:32.830 OK, in this lecture, we have discussed Alsup statement and logical operators. 07:33.370 --> 07:38.800 Now it's time to practice and the coming videos, the coding task and a little quiz are waiting for 07:38.800 --> 07:38.990 you. 07:39.730 --> 07:40.870 So let's go ahead.