notes.md

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5-5 1: What is the module, different formats of module technique, import, and export

The module is used to control the scope of the variable, function, class, etc. declaration in Typescript just like JavaScript.

By setting "module": "commonjs", "module": "ES6", "module": "ES2015" in the tsconfig.js file we can control our Typescript code compilation to Javascript versions.

5-5 2: Different types of Import and export statement

• using alias

  • import { *adder* as addTwo } from "./module";

• Wildcard import

  • import * as Methods from "./module";
  • * means everything. Meaning importing everything from the file
  • usage - Methods.myFunction()

• default export

  • front another file, export default avg; then use it like, import avg, { multiply } from "./module";, call it avg()

• default export using object

  • export default { adder, subtract, multiply, divide, avg };
  • import Jekono from "./module";
  • Jekono.adder(3, 4);

• taking the programs to different files then export default and then using like this -

  import addTwo from "./utils/adder"; // can name anything cause of default export
  import avg from "./utils/avg";
  import divide from "./utils/divide";
  import subtract from "./utils/subtract";

• re-export

  • When there are a lot of imports.
  • creating utils folder, creating the utility functions then creating index.js file and importing from there.

5-5 3: Know About utility Types

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Utility types are used for manipulating an existing type/interface.

• Pick

  • creates a new type by picking a single or multiple properties key (string or union of strings) from another type.
  • opposite of Omit.

• Omit

  • creates a new type by omitting/removing single or multiple properties from another type.
  • opposite of Pick.

• Partial

  • creates a new type by making all the properties optional of an existing type.
  • opposite of Required.

• Required

  • creates a new type by making all the properties required of an existing type.
  • opposite of Partial.

• Readonly

  • creates a new type by making all the properties readonly of an existing type. Just like readonly access modifiers.

• Record

  • Record is a shortcut to defining an object type with a specific key type and value type.
  • Index signatures can’t be used with literal types

  so we use Record to do this

  type MyObj = Record<"a" | "b" | "c", string>;

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5-5 4: How to use multiple interfaces as a type and create a model for a class

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