/TypeScript

Primary LanguageJavaScript

TypeScript

  1. Dynamic vs Static Typing

In dynamically typed languages, the types are associated with run-time values and not named explicitly in your code In statically typed languages, you explicitly assign types to variables, function parameters, return values, etc

Static Examples: Java, C, C++, Rust, Go Dynamic Examples: JavaScript, Python, Ruby, PHP

  1. PRO'S AND CON'S

PROS CONS
More Robust More Code To Write
Easily Spot Bugs More To Learn
Predictability Required Compilation
Readability Not True Static Typing
Popular

  1. Compiling TypeScript

    • TypeScript uses .ts and .tsx extensions
    • TSC (TypeScript Compiler) is used to compile .ts files down to JS
    • Can watch files and report errors at compile time
    • Many tools include TS compilation by default
    • Most IDEs have great support for TS
    • The tsconfig.json file is used to configure how TypeScript works

  2. Creating a config file

    1. tsc --init
    2. In tsconfig.json "target": "ES6" to change version of JS.
    3. "rootDir" is where ts files will reside
    4. "outDir" is where js files will reside

  3. Basic types

    1. number

    2. string

    3. boolean

    4. any -> dynamic type

    5. array -> <type>[]

      • Example: let ids: number[] = [1, 2, 3, 4, 5]
      • any as a type for a array is valid, it will support dynamic type.
      • tuple is when we want specific types elements to go in a specific order in an array.
      • Example: let person: [number, string, boolean] = [1, 'Brad', false ]

    6. union '|' -> to define more than 1 type to a variable / function parameter.

    7. enum

      • Enums allow a developer to define a set of named constants. Using enums can make it easier to document intent, or create a set of distinct cases. TypeScript provides both numeric and string-based enums.

      • just access any member as a property off of the enum itself, and declare types using the name of the enum

    8. Objects

      • Objects are like normal objects but we can define types for their properties.

      • type or interface can also be used to define types for the properties.

    9. Interface

      • Difference between a type and interface is that, we cannot use interface with union or primitives, i.e.
      + type Point = number | string;

- interface Point = number | string ;

      • ? in front of a type key (property) in an interface makes it optional.

      • We can make a property read-only by adding readonly prefix to it.

      • Syntax to add interface to a class: class <classname> implements <interface_name>

    10. Type Assertion

      • over-riding type of an entity while inheriting it.
      • way #1: <type>element
      • way #2: element as type

    11. Functions

      • Syntax: function name(param: type): return-type {...}
      • If there is no return type, use void as the return type.

    12. Class

      • constructor is used to assign values to properties of a class.
      • when extending a class (sub-class) super is used to pass values to the properties which are inherited from parent class.

    13. Generics

      • Makes array dynamic on the go.
      • <Type> / <T> is used to denote generic type.