Function d

TypeScript/StudyTypeScript/src/type_inference.ts:6–6

(x = 1)

let b  = [1, null]; // 通用类型推断
let c = {x: 1, y: 'a'}
let d = (x = 1) => x + 1;

// 上下文类型推断
// window.onkeydown = (event) =>{