嵌套在 for 循环外的 return 语句出现问题

Question

I amm new to javascript and am working through freecodecamp's resources (amongst other things). There was a challenge task to loop through phone contacts and I am sure some people will be familiar with it. I managed the task just fine, but am confused as to why the final return statement needs to exist outside the for loop, as opposed to an else statement for the outer if.

function lookUpProfile(name, prop){
  for (var i = 0; i < contacts.length; i++) {
    if (name === contacts[i].firstName) {
      if (prop === "lastName" || prop === "number" || prop === "likes") {
        return contacts[i][prop];
      }else{
        return "No such property"
      };
    }    
  }
  return "No such contact";
};

If I ever nested the final return statement (as an else) inside the for loop, the code would appear to go straight to this, even though the conditions for the initial if statement were true.

Can anyone please explain why? If you need any further information please let me know. I have tried searching google for why this might be the case but I haven't managed to find anything.

Thanks!

Answer 1

You don't wanna return "No such contact" just because comparing first element returns false. This will not work. Only after comparing and checking for all the elements in array you would know the contact doesn't exists. If the first contact doesn't match loop will return and no further comparisons will be done.

Answer 2

I've added an else to your example to be more explicit to hopefully make it more clear what is actually happening in the for loop. That else statement doesn't need to be there because the for loop would continue regardless.

function lookUpProfile(name, prop){
    for (var i = 0; i < contacts.length; i++) {
        if (name === contacts[i].firstName) {
            if (prop === "lastName" || prop === "number" || prop === "likes") {
                return contacts[i][prop];
            }
            else return "No such property";
        } else {
            continue;
        }  
    }
    return "No such contact";
};

If you were to place a return where the continue currently is you would never make it past the first contact.

Answer 3

You need to iterate over all the elements to make sure that there is no contact with matching name.