This document discusses type systems and TypeScript. It provides an overview of TypeScript's type system features including gradual typing, structural and generic types, distinct value and type namespaces, extensive type inference, control flow analysis, support for object-oriented and functional programming. It also discusses TypeScript's design goals of being open source, closely tracking the ECMAScript standard, innovating in its type system, having best-in-class tooling, lowering barriers to entry, and focusing on community.

1. Type Systems
@ddprrt • fettblog.eu

3. workingdraft.de
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4. technologieplauscherl.at
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5. technologieplauscherl.at
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scriptconf.org
@scriptconf
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6. technologieplauscherl.at
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scriptconf.org
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7. scriptconf.org

10. MEETUPS

13. Endlich kann ich Klassen schreiben!

17. = =
== ===

18. =
=
==
===
Turbo Pascal
Borland Delphi
C#
TypeScript

19. Anders Hejlsberg

23. GOSLING

24. You guys (at Microsoft)
still don't get it,
because it's sort of
Java with reliability,
productivity and
security deleted
- James Gosling
reliability
productivity

25. reliability productivity

26. Design goals

28. https://www.ecma-international.org/activities/Languages/Language%20overview.pdf

29. https://web.archive.org/web/20080723235906/http://ecmascript.org/es4/spec/evolutionary-programming-tutorial.pdf

30. ⭐ Open Source and Open Development
" Closely track ECMAScript standard
# Innovate in type system
$ Best of breed tooling
⏬ Continually lower barrier to entry
& Community, community, community

31. ⭐ Open Source and Open Development
" Closely track ECMAScript standard
# Innovate in type system
$ Best of breed tooling
⏬ Continually lower barrier to entry
& Community, community, community

32. ⭐ TypeScript IS JavaScript
⭐ Language innovation through ECMAScript
⭐ Type system innovation through use cases
⭐ Tooling as prime citizen
Non-goal: Apply a sound or "provably correct" type system. Instead, strike a balance
between correctness and productivity.

33. Type systems, oida!

34. ⛩ Gradual, structural, generic
( Distinct value / type namespaces
) Extensive type inference
* Control flow analysis
& Object-oriented and functional

35. Gradual, structural, generic

36. Duck typing

41. Type namespaces

42. primitive types
number
string
boolean
Symbol
Object
null
undefined

43. number
string
boolean
Symbol
Object
null
undefined
top types any
unknown

44. number
string
boolean
Symbol
Object
null
undefined
bottom types never

45. primitive types
number
string
boolean
Symbol
Object
null
undefined

46. primitive types
number
string
boolean
null
undefined

47. value types
number
string
boolean
null
undefined
true
false
-1
1000000
NaN
6
120.3
…
…
‘Hello world’
‘Baumi’

48. value types
true
false
-1
1000000
NaN
6
120.3
…
…
‘Hello world’
‘Baumi’null
undefined

49. value types
number
string
boolean
true
false
-1
1000000
NaN
6
120.3
…
…
‘Hello world’
‘Baumi’null
undefined

50. number |
string |
undefined
number
string
boolean
true
false
-1
1000000
NaN
6
120.3
…
…
‘Hello world’
‘Baumi’null
undefined

51. Intersection types
{ a: string }
{ b: string }
{
a: string,
b: string
}

52. Examples

53. fin