Map the Debris - treading verrry slowly

JavaScript
1

There is a lot going on here that I am trying to wrap my head around. In order to not confuse myself, I wanted to get the first testcase to pass before I make the code more robust for the 2nd (and subsequent) testcase(s).

When I run my current code in Atom/Chrome console, I get the following result (which I think is right):

FinalArray {name: “sputnik”, orbitalPeriod: 86400}

But in FCC, I get the following error:

orbitalPeriod([{name : "sputnik", avgAlt : 35873.5553}]) should return [{name: "sputnik", orbitalPeriod: 86400}].

What am I missing?

Thank you,

Your code so far

function orbitalPeriod(arr) {
  var GM = 398600.4418;
  var earthRadius = 6367.4447;

  let name = arr[0]["name"];
  let avgAlt = arr[0]["avgAlt"];

  //(earthRadius + avgAlt)^3:
  let firstCalc = Math.pow((earthRadius + avgAlt), 3);

  //firstCalc/GM:
  let secondCalc = firstCalc/GM;

  //sqrt of secondCalc:
  let thirdCalc = Math.sqrt(secondCalc);

  //final result:
  let finalResult = Math.round(thirdCalc * 2 * Math.PI);
  
  //present final result:
  function FinalArray(name, seconds){
    this.name = name;
    this.orbitalPeriod = seconds;
}

  var myFinalArray = new FinalArray(name, finalResult);

  console.log(myFinalArray);

}

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

Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/map-the-debris

2

Looks like you’re returning the object – but the test case is checking the object in the first position of an array…

1 Like
3

Oh yes I see. OK.

So then I created an arr and tried to push final result object to that array but am getting very odd result: 1 (just the number 1…).

New code:

function orbitalPeriod(arr) {
  var GM = 398600.4418;
  var earthRadius = 6367.4447;

  let finalArr = [];

  let name = arr[0]["name"];
  let avgAlt = arr[0]["avgAlt"];

  //(earthRadius + avgAlt)^3:
  let firstCalc = Math.pow((earthRadius + avgAlt), 3);

  //firstCalc/GM:
  let secondCalc = firstCalc/GM;

  //sqrt of secondCalc:
  let thirdCalc = Math.sqrt(secondCalc);

  //final result:
  let finalResult = Math.round(thirdCalc * 2 * Math.PI);

  //present final result:
  function FinalArray(name, seconds){
    this.name = name;
    this.orbitalPeriod = seconds;
}

  var myFinalArray = new FinalArray(name, finalResult);

  return finalArr.push(myFinalArray);

}

//orbitalPeriod([{name : "sputnik", avgAlt : 35873.5553}]);
4

So tell me – what does finalArr.push(...) actually return? Take a look at theMDN docs on Array.push(). That’s where your 1 is coming from.

You might want to do the finalArr.push(...) in one step, then return finalArr as a separate step.

1 Like
5

Thanks for all your help @snowmonkey.

My final code:

function orbitalPeriod(arr) {
  var GM = 398600.4418;
  var earthRadius = 6367.4447;

  let finalArr = [];

  for(var i = 0; i < arr.length; i++){
    let name = arr[i]["name"];
    let avgAlt = arr[i]["avgAlt"];

    //(earthRadius + avgAlt)^3:
    let firstCalc = Math.pow((earthRadius + avgAlt), 3);

    //firstCalc/GM:
    let secondCalc = firstCalc/GM;

    //sqrt of secondCalc:
    let thirdCalc = Math.sqrt(secondCalc);

    //final result:
    let finalResult = Math.round(thirdCalc * 2 * Math.PI);
    console.log("This is the final result: " + finalResult);

    //present final result:
    function FinalArray(name, seconds){
      this.name = name;
      this.orbitalPeriod = seconds;
    }

      var myFinalArray = new FinalArray(name, finalResult);

      finalArr.push(myFinalArray);
  };
  return finalArr;
}


//orbitalPeriod([{name: "iss", avgAlt: 413.6}, {name: "hubble", avgAlt: 556.7}, {name: "moon", avgAlt: 378632.553}])
//should return [{name : "iss", orbitalPeriod: 5557}, {name: "hubble", orbitalPeriod: 5734}, {name: "moon", orbitalPeriod: 2377399}].
6

Great work, looks good!

Now, can you think of a way to do the same thing without a for loop? Have you learned about a function that operates on an array, and is passed a function to perform on each member of that array? One that returns a new array of the same length?

Not saying your answer is wrong, just that you can handle the same problem in many ways. But… If 98 job applicants use a for loop and two use Array.map(), i’m paying attention to those two.

1 Like
7

I will try it and get back to you.

1 Like