Javascript - Interest calculator keeps returning undefined as output

Question

I'm a newbie JS developer that has been struggling with a particular problem for a while, it's kind of hard to explain(as seen from the title) so I'll show the problem together with my answers if that will help.

First create an array of objects called data with the following values:

1. Principal- 2500, time- 1.8, 2. Principal- 1000, time- 5,
2. Principal- 3000, time- 1,

3. Principal- 2000, time- 3

4. Write a function called "interestCalculator" that takes an array as a single argument and does the following:

   • If the principal is greater than or equal to 2500 and the time is greater than 1 and less than 3, then rate = 3
   • If the principal is greater than or equal to 2500 and the time is greater than or equal to 3, then rate = 4
   • If the principal is less than 2500 or the time is less than or equal to 1, then rate = 2
   • Otherwise, rate = 1; Calculate the interest for each individual object using the formula: (principal * rate * time) / 100.

The function should return an array of objects called 'interestData' and each individual object should have 'principal', 'rate', 'time' and 'interest' as keys with their corresponding values. Log the 'interestData' array to console BEFORE your return statement. Finally, call/execute the function and pass the 'data' array you created.

ANSWER:

 const Data = [
    {
        Principal: 2500,
        Time: 1.8
    },
    {
        Principal: 1000,
        Time: 5
    },
    {
        Principal: 3000,
        Time: 1
    },
    {
        Principal: 2000,
        Time: 3
    }
];

let rate;
 const interestCalculator = (array) =>{
     const interestData = array.map(item =>{
         const {Principal, Time} = item;
         if(Principal>=2500 && Time >= 1 && time < 3){
             rate = 3;
         }
         else if(Principal>=2500 && Time >= 3){
             rate = 4;
         }
         else if(Principal<2500 || Time <= 1){
             rate=2;
         }
         else{
             rate = 1;
         }

         const interest = (Principal * rate * Time)/100;

         item.interest = interest;
         item.rate= rate;
     });
     console.log(interestData);
     return interestCalculator();
 }

The above code returns "undefined" in the console. So I tried another way:

const interestCalculator = (item) =>{
    let rate;
    if(Principal>=2500 && Time >= 1 && time < 3){
        rate = 3;
    }
    else if(Principal>=2500 && Time >= 3){
        rate = 4;
    }
    else if(Principal<2500 || Time <= 1){
        rate = 2;
    }
    else{
        rate = 1;
    }
const interest = (Principal * rate * Time)/100;
const interestData = [item.Principal, item.rate, item.Time, item.interest];
console.log (interestData);
return interestCalculator();

}

Still undefined...I tried different methods(foreach(), arr.push()) that I currently know of but to no avail. Im pretty stumped and any help will greatly be appreciated. Sorry for the long post. Thank you.

Answer 1

You need to return item from inside the .map() and call the interestCalculator with Data as an argument like below:

const Data = [{
    Principal: 2500,
    Time: 1.8
  },
  {
    Principal: 1000,
    Time: 5
  },
  {
    Principal: 3000,
    Time: 1
  },
  {
    Principal: 2000,
    Time: 3
  }
];

let rate;
const interestCalculator = (array) => {
  const interestData = array.map(item => {
    const {
      Principal,
      Time
    } = item;
    if (Principal >= 2500 && Time >= 1 && Time < 3) {
      rate = 3;
    } else if (Principal >= 2500 && Time >= 3) {
      rate = 4;
    } else if (Principal < 2500 || Time <= 1) {
      rate = 2;
    } else {
      rate = 1;
    }

    const interest = (Principal * rate * Time) / 100;

    item.interest = interest;
    item.rate = rate;
    
    return item;
  });
  
  return interestData;
}

console.log(interestCalculator(Data));