Type Inference

Code

let x = 10;        // number
let s = "hello";   // string
let arr = [1, 2];  // number[]
let obj = { a: 1, b: "x" }; // { a: number; b: string }

// Function return type inference
function add(a: number, b: number) {
  return a + b;  // Infers return number
}

// Destructure inference
const { a, b } = obj;  // a: number, b: string

// const assertion as literal
const config = { mode: "dev" } as const;  // { readonly mode: "dev" }

Explanation

TS automatically infers types based on context, reducing explicit annotations.

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