function makeStudentsReport(data) {

 return data.map( d => `${d.name} : ${d.grade}`);

}

/* From here down, you are not expected to
   understand.... for now :)

   Nothing to see here!

*/

// tests

function testIt() {
  const testData = [
    { name: 'Jane Doe', grade: 'A' },
    { name: 'John Dough', grade: 'B' },
    { name: 'Jill Do', grade: 'A' },
  ];

  const expectations = ['Jane Doe: A', 'John Dough: B', 'Jill Do: A'];

  const results = makeStudentsReport(testData);

  if (!(results && results instanceof Array)) {
    console.error('FAILURE: `makeStudentsReport` must return an array');
    return;
  }
  if (results.length !== testData.length) {
    console.error(
      'FAILURE: test data had length of ' +
        testData.length +
        ' but `makeStudentsReport` returned array of length ' +
        results.length
    );
    return;
  }
  for (let i = 0; i < expectations.length; i++) {
    let expect = expectations[i];
    if (
      !results.find(function(item) {
        return item === expect;
      })
    ) {
      console.error(
        'FAILURE: `makeStudentsReport` is not ' + 'producing expected strings'
      );
      return;
    }
  }
  console.log('SUCCESS: `makeStudentsReport` is working');
}

testIt();