function isIsogramOne(str) {

    let strLower = str.toLowerCase(); // convert to lowercase
    let charArr = strLower.split(''); // split into array 
    let result = []; // create empty array to store unique characters

    for (let i = 0; i < charArr.length; i++) { // loop through array
        if (result.indexOf(charArr[i]) === -1) { // if chraacter is not in array
            result.push(charArr[i]); // push character to array 
        }
    }
    return result.length === charArr.length;
}

function isIsogramTow(str) {
    return str.toLowerCase().split('').filter((item, index, array) =>
        array.indexOf(item) === index).length === str.length;
}