Google Apps Script that will take a value from a user and compare it to values stored in an array.

checkAgainstArray.gs

function myFunction() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet(); 
  var nameArray = ["Joseph", "Elizabeth", "Roman", "Sophia"];

  // GET VALUE FROM USER 

  let valueFromUser = Browser.inputBox("Who are you looking for?");
  
  Logger.log(valueFromUser);

  var answerCell = sheet.getRange("A1"); 

  Logger.log(nameArray);
  Logger.log(nameArray.indexOf(valueFromUser));

  if (nameArray.indexOf(valueFromUser) >= 0) {
    answerCell.setValue("The name is in the array");
  } else {
    answerCell.setValue("That name is NOT in the array");
    answerCell.setBackground('red');
  }
}