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curriculum/challenges/english/blocks/workshop-space-mission-roster/694c9c186c089f7bdff0f3c6.md

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--description--

Generally, it is good practice to validate your input(s) inside a function. Use a for loop to iterate through the crew array and check whether any member already has the same id as the input astronaut. If a duplicate is found, log the error message console.log("Duplicate ID: " + astronaut.id) and then call return to exit the function early.

Here is an example of this commonly used technique:

js
if (existingMember.id === newMember.id) {
    console.log("Duplicate ID: " + newMember.id);
    return;
}

--hints--

Your function should use a for loop to scan existing crew members (any valid for (...) form is fine).

js
assert.match(__helpers.removeJSComments(code), /for\s*\([^)]*\)/);

Inside the for loop, you should check for a duplicate id. If one is found, log "Duplicate ID: " + astronaut.id" to the console and then call return to exit the function.

js
const spy = __helpers.spyOn(console, "log");

try {
  const crewWithDuplicate = [
    { id: 1 },
    { id: 2 },
    { id: 3 },
    { id: 4 },
    { id: 3 }
  ];
  addCrewMember(crewWithDuplicate, { id: 3 });

  assert.lengthOf(
    spy.calls,
    1,
    "Duplicate ID input should trigger exactly one console.log and then exit"
  );
  assert.match(
    spy.calls[0][0],
    /duplicate\s+id\s*:\s*3/i,
    "Console message should mention 'duplicate id'"
  );

} catch (err) {
  assert.fail(err);
} finally {
  spy.restore();
}

When given valid inputs, your addCrewMember function should not invoke a console.log() error message or an early return exit.

js
const spy = __helpers.spyOn(console, "log");

try {
  const crewNoDuplicate = [
    { id: 1 },
    { id: 2 },
    { id: 3 },
    { id: 4 }
  ];
  addCrewMember(crewNoDuplicate, { id: 5 });

  assert.lengthOf(
    spy.calls,
    0,
    "A truly new astronaut should produce zero console.log calls"
  );

} catch (err) {
  assert.fail(err);
} finally {
  spy.restore();
}

--seed--

--seed-contents--

js
const squad = [];

const firstAstronaut = {
  id: 1,
  name: "Andy",
  role: "Commander",
  isEVAEligible: true,
  priority: 3
};

function addCrewMember(crew, astronaut) {
--fcc-editable-region--

--fcc-editable-region--
}