var guestList = ['Gabe', 'name2', 'name3', 'name4', 'name5'] var guestName = prompt('Hello, what is your name') var range = guestList.slice(0, guestList.length) if (guestList.includes(range)) { alert(`Hello ${guestName} and welcome to EVENT NAME`) } else { alert(`Hello ${guestName}, you are not on the guest list`) }Eche un vistazo a esa línea de su código var range = guestList.slice(0, guestList.length) . Ahora el range es una sub-matriz de guestList y está tratando de verificar en guestList si incluye el range de elementos que no es cierto.
Creo que estás tratando de hacer esto:
var guestList = ['Gabe', 'name2', 'name3', 'name4', 'name5'] var guestName = prompt('Hello, what is your name') if (guestList.includes(guestName)) { alert(`Hello ${guestName} and welcome to EVENT NAME`) } else { alert(`Hello ${guestName}, you are not on the guest list`) }Elimine el range porque es inútil y reemplace el range en esta línea con guestName
if (guestList.includes(guestName)) {.... Prompt() devuelve un valor que es lo que haya ingresado el usuario.
var guestList = ['Gabe', 'name2', 'name3', 'name4', 'name5'] var guestName = prompt('Hello, what is your name') /* Add this line if you want the comparison to be case insensitive */ // guestList = guestList.map(name => name.toLowerCase()); /* And replace guestName with guestName.toLowerCase() in the "if" statement as well. */ if (guestList.includes(guestName)) { alert(`Hello ${guestName} and welcome to EVENT NAME`) } else { alert(`Hello ${guestName}, you are not on the guest list`); }¿Es esto lo que quieres?
var guestList = ['Gabe', 'name2', 'name3', 'name4', 'name5'] var guestName = prompt('Hello, what is your name') if (guestList.includes(guestName)) { alert(`Hello ${guestName} and welcome to EVENT NAME`) } else { alert(`Hello ${guestName}, you are not on the guest list`) }