Counting below / par elements from an array - JavaScript

We are required to write a function that counts how many elements in an array are below or at/above a given number.

Following is our array of Numbers ?

const array = [54,54,65,73,43,78,54,54,76,3,23,78];

For example, if the number is 60, there should be 7 elements below it ?

54,54,43,54,54,3,23

and 5 elements at or above it ?

65,73,78,76,78

Using Array.reduce() Method

The reduce() method processes each array element and accumulates the count of elements below and at/above the threshold.

const array = [54,54,65,73,43,78,54,54,76,3,23,78];

const belowParNumbers = (arr, num) => {
    return arr.reduce((acc, val) => {
        const legend = ['par', 'below'];
        const isBelow = val 

{ below: 3, par: 9 }
{ below: 7, par: 5 }
{ below: 8, par: 4 }


How It Works

The function uses a clever technique:

• val returns true or false
• +isBelow converts boolean to number: true becomes 1, false becomes 0
• legend[1] is "below", legend[0] is "par"
• Each element increments either the "below" or "par" counter

Alternative: Using filter() Method

const array = [54,54,65,73,43,78,54,54,76,3,23,78];

const countBelowPar = (arr, num) => {
    const below = arr.filter(val => val  val >= num).length;
    return { below, par };
};

console.log(countBelowPar(array, 60));
console.log(countBelowPar(array, 70));

{ below: 7, par: 5 }
{ below: 8, par: 4 }

Comparison

Conclusion

Use reduce() for better performance with large arrays, or filter() for simpler, more readable code. Both methods effectively count elements below and at/above a threshold value.