Elegant Error Handling Code Samples

process-csv-data-helpers.js

function splitCSVToRows(csvData) {
    // There should always be a header row... so if there's no
    // newline character, something is wrong.
    return (csvData.indexOf('\n') < 0)
        ? left('No header row found in CSV data')
        : right(csvData.split('\n'));
}

function processRows(headerFields, dataRows) {
    // Note this is Array map, not Either map.
    return dataRows.map(row => processRow(headerFields, row));
}

function showMessages(messages) {
    return `<ul class="Messages">${messages.join('\n')}</ul>`;
}