Typescript

Basic video: https://www.youtube.com/watch?v=WBPrJSw7yQA. Video for react: https://www.youtube.com/watch?v=NjN00cM18Z4.

6 flashcards · Programming Languages · by lakesare

1. Declare a variable of type number.

   const hi: number = 3;

2. Write 2 ways to declare an array of strings.

   let marks: string[] = [80, 85, 75]; let marks: Array<string> = [80, 85, 75];

3. enum Color { red, green }; const rrr: Color = Color.green; console.log(rrr); What is the output?

   => 1. It was compiled into: "use strict"; var Color; (function (Color) { Color[Color["red"] = 0] = "red"; Color[Color["green"] = 1] = "green"; })(Color || (Color = {})); const rrr = Color.green; console.log({ rrr, aaa });

4. Define a type that can be either number or boolean.

   let me: number | boolean; me = 20; me = true;

5. What does ? achieve?

   It makes num2 optional. In Js: if you don't pass a variable it will be undefined. In Typescript: if you don't pass a variable, error will be raised!

6. Factor out type: