1
00:00:02,380 --> 00:00:10,670
So what is Times called What is it all about why would we use it typescript is a javascript superset.

2
00:00:10,860 --> 00:00:12,270
Now what does this mean.

3
00:00:12,280 --> 00:00:16,360
It means that typescript is in the end a language a programming language.

4
00:00:16,390 --> 00:00:21,010
Building up on javascript it's not a brand new language.

5
00:00:21,010 --> 00:00:27,520
Instead it takes the javascript language and adds new features and advantages to it.

6
00:00:27,520 --> 00:00:32,080
It makes writing javascript code easier and more powerful.

7
00:00:32,080 --> 00:00:40,090
You could say but we have one huge disadvantage typescript can't be executed by javascript environments

8
00:00:40,120 --> 00:00:48,670
like the browser browsers can't execute TypeScript and for example note J.S. also can't execute typescript

9
00:00:48,940 --> 00:00:53,990
soda environments where we can execute javascript don't support typescript.

10
00:00:54,130 --> 00:01:00,770
What's the idea behind typescript then it's a better version of JavaScript and we can't use it.

11
00:01:00,790 --> 00:01:05,990
Well not quite typescript is a programming language but it's also a tool.

12
00:01:06,130 --> 00:01:14,470
It's a powerful compiler which you run over your code to compile your typescript code to javascript.

13
00:01:14,470 --> 00:01:21,790
So what you get as a result when writing code in typescript is javascript but you didn't write that

14
00:01:21,790 --> 00:01:28,480
JavaScript code you wrote typescript code with all the new features and all the advantages and you get

15
00:01:28,570 --> 00:01:30,700
normal javascript code.

16
00:01:30,700 --> 00:01:37,450
Well that of course brings up one important question how can typescript add new features if what you

17
00:01:37,450 --> 00:01:40,860
get in the end is regular javascript.

18
00:01:40,870 --> 00:01:47,700
And the answer is the typescript compiler compiles these new features to JavaScript work arounds.

19
00:01:47,770 --> 00:01:54,290
So in the end it might give you a nicer syntax an easier way of doing something and it will then compile

20
00:01:54,290 --> 00:02:02,290
that nicer easier way to a more complex javascript snippet which you would have to write otherwise so

21
00:02:02,290 --> 00:02:03,250
it's not magic.

22
00:02:03,250 --> 00:02:10,630
Of course it can't add what's not possible at all in the javascript language but it can add new features

23
00:02:10,630 --> 00:02:14,850
that simply are easier to use nicer syntax things like this.

24
00:02:15,160 --> 00:02:20,980
In addition types of course does one important thing which the name already implies.

25
00:02:20,980 --> 00:02:28,360
It adds types it adds a feature to these javascript language add which will have a close look in a second

26
00:02:28,810 --> 00:02:36,550
which will actually give you as a developer an opportunity of identifying errors in your code earlier

27
00:02:36,820 --> 00:02:41,300
before your script runs and the error occurs at runtime in the browser.

28
00:02:41,410 --> 00:02:46,660
So it does not only give you some new features and nicer ways of doing something.

29
00:02:46,750 --> 00:02:54,130
It also gives you extra error checking where errors which you would otherwise get as runtime errors

30
00:02:54,520 --> 00:02:58,300
can be caught and fixed early during development.

31
00:02:58,390 --> 00:03:06,100
So why would we use typescript consider disk sample a fairly simple javascript function which adds to

32
00:03:06,100 --> 00:03:06,760
numbers.

33
00:03:06,760 --> 00:03:12,580
Now when I call it please notice that I'm passing in two strings instead of two numbers and I'll show

34
00:03:12,580 --> 00:03:18,130
you a real example where it's something like this could happen realistically in just a second.

35
00:03:18,130 --> 00:03:23,080
So we're calling this function with two strings and as a result what you would actually get here is

36
00:03:23,080 --> 00:03:29,740
probably an unwanted behavior because if you add two strings javascript will come candidate the strings

37
00:03:30,100 --> 00:03:32,790
instead of doing a mathematical calculation here.

38
00:03:32,830 --> 00:03:39,040
So the result would not be 5 but 20 free concatenated string of the two numbers.

39
00:03:39,040 --> 00:03:41,720
This is an error you could have in JavaScript.

40
00:03:41,770 --> 00:03:43,510
It's not a technical error.

41
00:03:43,600 --> 00:03:51,100
You probably won't get a runtime error but you have a logical mistake in your code and that of course

42
00:03:51,100 --> 00:03:55,900
can lead to huge problems in the web applications you're writing with JavaScript.

43
00:03:55,930 --> 00:03:59,370
Now of course in JavaScript we have mitigation strategies.

44
00:03:59,380 --> 00:04:05,390
We could add an if check in the function to check the types of DB inputs at runtime.

45
00:04:05,470 --> 00:04:11,430
We could also validate and sanitize user input and whilst we might want to do all of that it would also

46
00:04:11,440 --> 00:04:15,590
be nice if we could catch errors like this during development already.

47
00:04:15,910 --> 00:04:22,510
And thankfully this is possible with typescript because developers can write invalid code here and introduce

48
00:04:22,510 --> 00:04:28,330
bugs like this in javascript and with typescript we have a tool that helps us write better code and

49
00:04:28,330 --> 00:04:30,040
avoid such problems.

50
00:04:30,100 --> 00:04:31,680
So let's have a closer look at this.