A reasonably robust, relatively comprehensible CSV / DSV parser, <1 KB minified, for when you don't want to import a giant library. MIT Licensed.

parse-csv.ts

export type CSVOptions = Partial<{
    fieldSeparator: string,
    rowSeparator: string,
    quote: string,
    trimFields: boolean,
    sanitizeRowSeparators: boolean,
}>;

/**
 * Converts a CSV string to an array of arrays.
 *
 * Adapted from http://code.google.com/p/csv-to-array/ v2.1 by Daniel Tillin
 * under the MIT License: https://opensource.org/licenses/mit-license.php
 *
 * Some test cases can be found at https://codepen.io/IceCreamYou/pen/JveBmy
 *
 * @param inputString
 *   The CSV file to parse, as a string.
 * @param options
 *   Options describing how to parse the CSV input:
 *   - fieldSeparator: The delimiter between fields
 *   - rowSeparator: The delimiter between rows; can be `\r`, `\n`, or `\r\n`
 *   - quote: The field escape character
 *   - trimFields: Whether to ignore whitespace around fields
 *   - sanitizeRowSeparators: Whether to accept multiple line ending formats
 */
export function csvToArray(inputString: string, options: CSVOptions = {}) {
    const { fieldSeparator, rowSeparator, quote, trimFields, sanitizeRowSeparators } = {
            fieldSeparator: ',',
            rowSeparator: '\n',
            quote: '"',
            trimFields: false,
            sanitizeRowSeparators: true,
            ...options,
        },
        rowSepChar1 = rowSeparator.charAt(0),
        rowSepChar2 = rowSeparator.charAt(1);
    if (sanitizeRowSeparators) {
        inputString = inputString.replace(/\r\n|\r/g, rowSeparator);
    }

    const outputArray = [['']],
        inputLength = inputString.length;
    for (let strPos = 0, rowIndex = 0, fieldIndex = 0, foundQuote = false; strPos < inputLength; strPos++) {
        const currentCharacter = inputString.charAt(strPos);
        switch (currentCharacter) {
            case quote:
                // Found an escaped quote (""); add to field
                if (foundQuote && inputString.charAt(strPos + 1) === quote) {
                    outputArray[rowIndex][fieldIndex] += quote;
                    strPos++;
                }
                // Start or end a quoted field
                else {
                    foundQuote = !foundQuote;
                }
                break;
            case fieldSeparator:
                // Found a new field
                if (!foundQuote) {
                    // Trim the previous field
                    if (trimFields) {
                        outputArray[rowIndex][fieldIndex] = outputArray[rowIndex][fieldIndex].trim();
                    }
                    // Start a new field
                    outputArray[rowIndex][++fieldIndex] = '';
                }
                // We're in a quoted field so the field separator is not a special character; add it to the field
                else {
                    outputArray[rowIndex][fieldIndex] += currentCharacter;
                }
                break;
            case rowSepChar1:
                // Found a row delimiter
                if (!foundQuote && (!rowSepChar2 || rowSepChar2 === inputString.charAt(strPos + 1))) {
                    // Trim the previous field
                    if (trimFields) {
                        outputArray[rowIndex][fieldIndex] = outputArray[rowIndex][fieldIndex].trim();
                    }
                    // Start a new row
                    outputArray[++rowIndex] = [''];
                    fieldIndex = 0;
                    // If the rowSeparator is \r\n, the current character is \r; skip the \n
                    if (rowSepChar2) strPos++;
                }
                // We're in a quoted field so the row separator is not a special character; add it to the field
                else {
                    outputArray[rowIndex][fieldIndex] += currentCharacter;
                }
                break;
            // Found a non-special character; add it to the field
            default:
                outputArray[rowIndex][fieldIndex] += currentCharacter;
        }
    }

    // Return the result
    return outputArray;
}