Merge two arrays

JavaScript

// Merge but don't remove the duplications
const merge = (a, b) => a.concat(b)
// Or
const merge = (a, b) => [...a, ...b]

// Merge and remove the duplications
const merge = (a, b) => [...new Set(a.concat(b))]
// Or
const merge = (a, b) => [...new Set([...a, ...b])]

TypeScript

// Merge but don't remove the duplications
const merge = <T,_>(a: T[], b: T[]): T[] => a.concat(b)
// Or
const merge = <T,_>(a: T[], b: T[]): T[] => [...a, ...b]

// Merge and remove the duplications
const merge = <T,_>(a: T[], b: T[]): T[] => [...new Set(a.concat(b))]
// Or
const merge = <T,_>(a: T[], b: T[]): T[] => [...new Set([...a, ...b])]