One-line UUID v4

// Generate an RFC 4122 v4 UUID using the Web Crypto API
const uuid = () =>
    ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, (c) =>
        (
            +c ^
            (crypto.getRandomValues(new Uint8Array(1))[0] & (15 >> (+c / 4)))
        ).toString(16)
    )

console.log(uuid())