JavaScript
const rgbToHex = (red, green, blue) => `#${((1 << 24) + (red << 16) + (green << 8) + blue).toString(16).slice(1)}`
const rgbToHex = (red, green, blue) => `#${[red, green, blue].map((v) => v.toString(16).padStart(2, '0')).join('')}`
TypeScript
const rgbToHex = (red: number, green: number, blue: number): string => `#${((1 << 24) + (red << 16) + (green << 8) + blue).toString(16).slice(1)}`
const rgbToHex = (red: number, green: number, blue: number): string => `#${[red, green, blue].map((v) => v.toString(16).padStart(2, '0')).join('')}`
Examples
rgbToHex(0, 255, 255)