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How can I find remaining percentages if one or two percentages are known

Consider the following Objects:

// Example 1

{
    gradeA: 100,
    gradeB: 'No-Data',
    gradeC: 'No-Data'
}
// Example 2

{
   gradeA: 50,
   gradeB: 40,
   gradeC: 'No-Data'
}
// Example 3

{
   gradeA: 75,
   gradeB: 'No-Data',
   gradeC: 'No-Data'
}

They represent a percentage, i.e. the sum of all three grades will be exactly 100. How can we interpolate the keys with 'No-Data' whenever their values can be calculated?

Expected Results:

// Example 1

{
    gradeA: 100,
    gradeB: 0,
    gradeC: 0
}
// Example 2

{
   gradeA: 50,
   gradeB: 40,
   gradeC: 10
}
// Example 3

{
   gradeA: 75,
   gradeB: 'No-Data',
   gradeC: 'No-Data'
}

// Note: This one can't be figured out so we leave it as is.

My solution in pseudo-code:

function interpolate(obj) {
    // If only one key is a number:
    //    The value is 100:
    //        Set the other two keys to 0 and return the obj.
    //    The value is less than 100:
    //        return obj unchanged.
    // If only one key is not a number:
    //    set that key to the sum of the two numbers minus 100 and return the obj.
}

There are two main questions here:

  1. How do I find out how many and which keys are 'No-Data'.
  2. Can I rearrange the control flow to be more efficient?

In reality, these Objects are inside an Array, but I’m sure I can figure that stuff out myself.

Answer

  1. You can use something like this to filter for a key given a value (in your case No-Data).

let keys = Object.keys(obj).filter(k=>obj[k]===value);

Just count the number of items in the array to see how many you have.

  1. Your control flow is fine, it will be readable and its efficiency depends on how efficient you are at counting the number of occurances of No-Data. Tip: If you are trying to be as efficient as possible, you don’t need to keep finding occurrences of No-Data after you find 2 🙂

Ps. There are a few issues with the other code that was posted that will probably stop you from getting full points if you turn it in 🙂