HackerRank Day 2: Conditional Statements: If-Else 10 days of javascript solution

In this HackerRank Day 2: Conditional Statements: If-Else problem you need to Complete the getGrade(score) function in the editor. It has one parameter: an integer, score, denoting the number of points Julia earned on an exam. It must return the letter corresponding to her grade according to the rules:

HackerRank Day 2: Conditional statements If-Else 10 days of javascript problem solution.

'use strict';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('n').map(string => {
        return string.trim();
    });
    
    main();    
});

function readLine() {
    return inputString[currentLine++];
}

function getGrade(score) {

   if(score > 25 && score <= 30){
        return("A");
    }else if(score > 20 && score <= 25){
        return("B");
    }else if(score > 15 && score <= 20){
        return("C");
    }else if(score > 10 && score <= 15){
        return("D");
    }else if(score > 5 && score <= 10){
        return("E");
    }else if(score > 0 && score <= 5){
        return("F");
    }
    
}

function main() {
    const score = +(readLine());
    
    console.log(getGrade(score));
}