HELP, Why the function returns an undefined ? 😫

JavaScript
1

Please consider the code below:

The Code 
function orbitalPeriod(arr) {
  const GM = 398600.4418;
  const earthRadius = 6367.4447;
  return arr.map(({ name, avgAlt }) => {
    const earth = earthRadius + avgAlt;
/*here*/orbitalPeriod = Math.round(2 * Math.PI * Math.sqrt(Math.pow(earth, 3)/GM));
    return { name, orbitalPeriod };
  });
}

Why the function returns orbitalPeriod even though it was not declared? can someone explain please?!

2

It was declared. Your function is called orbitalPeriod. Then within the function, you reassign it to a number, so you can’t use the function a second time:

function orbitalPeriod(arr) {
  const GM = 398600.4418;
  const earthRadius = 6367.4447;
  return arr.map(({ name, avgAlt }) => {
    const earth = earthRadius + avgAlt;

    console.log('within 1', orbitalPeriod) // function
/*here*/orbitalPeriod = Math.round(2 * Math.PI * Math.sqrt(Math.pow(earth, 3)/GM));
    console.log('within 1', orbitalPeriod) // number

    return { name, orbitalPeriod };
  });
}
console.log('outside 1', orbitalPeriod) // function

/* first function call */
orbitalPeriod([{name : "sputnik", avgAlt : 35873.5553}]);

console.log('outside 2', orbitalPeriod) // number

/* second function call */
orbitalPeriod([{name : "sputnik", avgAlt : 35873.5553}]); 
// Uncaught TypeError: orbitalPeriod is not a function
1 Like
3

Thank you very much for explaining :heart: