Array of names in a function?

Question

/**
* @param {Array<string>} arrayOfPeople - an array of people's names
* @returns {number} the length of the given array of names
*/

function numberOfPeople(arrayOfPeople) {
return arrayOfPeople = ["Alex", "Beau", "Carlos", "Dustin"];

}

console.log(numberOfPeople(arrayOfPeople.length));
//says arrayOfPeople is undefined?