TypeScript - All About Types - inference

Programming TypeScript
Making Your JavaScript Applications Scale
楽天ブックス 紀伊國屋書店

開発環境

• macOS Mojave - Apple (OS)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• TypeScript (プログラミング言語)
• Node.js(JavaScriptの実行環境)

Programming TypeScript: Making Your JavaScript Applications Scale (Boris Cherny(著)、O'Reilly Media)のChapter 3(All About Types)、Exercises(44)1の解答を求めてみる。

コード

TypeScript

let a = 1042 // number
let b = 'apples and oranges' // string
const c = 'pineapples' // "pineapples"
let d = [true, true, false] // boolean[]
let e = {type: 'ficus'} // {type:string}
let f = [1, false] // (number | boolean)[]
const g = [3] // number[]
let h = null // any
let values = [a, b, c, d, e, f, g, h]

values.forEach(_ => console.log(typeof(_), _))

入出力結果(Bash、cmd.exe(コマンドプロンプト)、Terminal)

$ ts-node src/index.ts 
number 1042
string apples and oranges
string pineapples
object [ true, true, false ]
object { type: 'ficus' }
object [ 1, false ]
object [ 3 ]
object null
$