let availableData = "Hello, Hi, Wassup";
let desiredData = replaceCommaLine(availableData);
function replaceCommaLine(data) {
    //convert string to array and remove whitespace
    let dataToArray = data.split(',').map(item => item.trim());
    //convert array to string replacing comma with new line
    return dataToArray.join("\n");
}
console.log(desiredData);