Build validation functions:
const isValidEmail = email =>
email && email.includes("@")
const isValidPassword = password =>
password && password.length >= 8
const isValidAge = age =>
typeof age === "number" && age >= 0 && age <= 150
function validateUser(email, password, age) {
if (!isValidEmail(email)) return "Invalid email"
if (!isValidPassword(password)) return "Password too short"
if (!isValidAge(age)) return "Invalid age"
return "Valid"
}
console.log(validateUser("test@example.com", "secret123", 25))
// Valid