Characters in Range - Miro's version

function solution(firstChar, lastChar) {

    let first = getNumberValue(firstChar);
    let last = getNumberValue(lastChar);

    let min = Math.min(first, last);
    let max = Math.max(first, last);

    let allSymbols = getCharsInRange(min, max);

    console.log(joinSymbols(allSymbols, " "));

    function getNumberValue(char) {
        return char.charCodeAt(0);
    }

    function getCharValue(number) {
        return String.fromCharCode(number);
    }

    function getCharsInRange(start, end) {
        let characters = [];

        for (let i = (start + 1); i < end; i++) {
            let symbol = getCharValue(i);
            characters.push(symbol);
        }

        return characters;
    }

    function joinSymbols(arr, separator) {
        let result = "";
        for (let index in arr) {
            let character = arr[index];

            if (index <= (arr.length - 2)) {
                result += `${character}${separator}`;
            } else {
                result += character;
            }
        }
        return result;
    }
}