makePercent.js

function makePercent(inputArr) {
    const sum = inputArr.reduce((sum, next) => sum + parseFloat(next), 0);
    return inputArr.map(v => (parseFloat(v) / sum * 100).toFixed(3));
}

// time complexity O(2n)
// space complexity O(n+1)
// array length must be lower than 10.000.000 (10 millions) to make it run under 5s