JavaScript 意外的未定义值 [已关闭]

问：

我正在运行以下 JavaScript 代码：

// Return true if the given username and password are in the database,
// false otherwise.
function validCredentials(enteredUsername, enteredPassword) {
   
   // Database of usernames and passwords
   let usernames = ["smith",  "tron",      "ace",      "ladyj",    "anon"];
   let passwords = ["qwerty", "EndOfLine", "year1942", "ladyj123", "PASSWORD"];
   
   // Search the usernames array for enteredUsername 
   
   // Only return true if the enteredUsername is in username, and the
   // same location in passwords is enteredPassword
   if (usernames.includes(enteredUsername)){
      var correctPassword = passwords[usernames.indexOf(enteredUsername)];
      if(enteredPassword == correctPassword){
         return true;
         }    
      }
      else {
         return false;
      }  
}


console.log("Login for ladyj: " + validCredentials("ladyj", "ladyj123"));  // true
console.log("Login for ace: " + validCredentials("ace", "wrong"));  // false
console.log("Login for jake: " + validCredentials("jake", "???"));  // false

我期待console.log（“ace的登录：” + validCredentials（“ace”，“错误”））;返回 false，但它返回 undefined。谁能告诉我出了什么问题？