TypeScript - Loop return gets skipped and base condition is returned-CodePudding

I have a custom object that is defined as following (names and properties have been simplified to avoid confidential information leakage):

type T = {
  id: number;
  title: string;
};

This type is used to create a list of Ts like so:

const IT: StringMap<T> = {
  a: {
    id: 0,
    title: 'foo',
  },
  b: {
    id: 1,
    title: 'bar',
  },
  c: {
    id: 2,
    title: 'foobar',
  },
}

I need a way to be able to retrieve one of these T type objects based on their id. So I created the following function:

const getTUsingId = (ts: StringMap<T>, id: number): T => {
  Object.values(ts).forEach((t: T) => {
    if (t.id === id) {
      return t
    }
  });

  // This is as a safeguard to return a default value in case an invalid id is passed
  return ts['a'] 
}

For whatever reason, this function will always return ts['a'] regardless of what id I pass to it. Console logging t.id === id even returns true but it still carries on until the end of the ts map!

Any help is highly appreciated!

CodePudding user response：

return won't break out of your loop. You need to use a plain for loop:

const getTUsingId = (ts: StringMap<T>, id: number): T => {
  for (const t of Object.values(ts)) {
    if (t.id === id) {
      return t
    }
  }

  return ts['a'] 
}

CodePudding user response：

the forEach callback is for performing an action on every element in the array, it's return isn't used for termination, what you want is filter, find or a regular for loop

Object.values(ts).filter((t: T) => {
  return t.id === id;
});

return all values where the id matches as a fresh array, you would use this if there was a possibility of multiple match, you would then need to parse the returned array to decide which match was correct

Object.values(ts).find((t: T) => {
  return t.id === id;
});

return only the first matching value

for(const t of Object.values(ts))
  if (t.id === id) {
    return t
  }
});

my preference would be find

const getTUsingId = (ts: StringMap<T>, id: number): T => {
  return Object.values(ts).find((t: T) => t.id === id) ?? ts['a'] 
}