Transform JS Array of CSV string

arrayToCsvString.js

/**
 * Transform an array of objects in javascript into a single csv string with the header as the first line
 *
 * Works on any javascript version above ES6 (2015)
 * 
 * @param array {any[]}
 * @param columnDelimiter {string}
 * @param quoteChar {string}
 * @param newline {string}
 * @returns {string}
 */
function arrayToCsvString(array, columnDelimiter = ',', quoteChar = '"', newline = '\n') {
    const columnNameList = [];
    for (const obj of array) {
        if (typeof obj !== 'object') {
            continue;
        }
        for (const property in obj) {
            if (columnNameList.indexOf(property) === -1) {
                columnNameList.push(property);
            }
        }
    }
    function transformColumnValueToCsvColumn(value) {
        if (value === null || value === undefined) {
            return '';
        }
        if (typeof value !== 'string') {
            value = value.toString();
        }
        if (value.includes(columnDelimiter) || value.includes(quoteChar) || value.includes(newline)) {
            return quoteChar + value.split(quoteChar).join(quoteChar + quoteChar) + quoteChar;
        }
        return value;
    }
    const lines = [
        columnNameList.map(columnName => transformColumnValueToCsvColumn(columnName)).join(columnDelimiter)
    ];
    for (const obj of array) {
        if (typeof obj === 'object') {
            const line = [];
            for (const property of columnNameList) {
                line.push(transformColumnValueToCsvColumn(obj[property]));
            }
            lines.push(line.join(columnDelimiter));
        }
    }
    return lines.join(newline);
}

arrayToCsvString.ts

/**
 * Transform a array of objects into a single csv string with the header as the first line
 * @param array
 * @param columnDelimiter
 * @param quoteChar
 * @param newline
 * @returns {string}
 */
function arrayToCsvString(array: any[], columnDelimiter = ',', quoteChar = '"', newline = '\n'): string {
    const columnNameList: string[] = [];
    for (const obj of array) {
        if (typeof obj !== 'object') {
            continue;
        }
        for (const property in obj) {
            if (!columnNameList.includes(property)) {
                columnNameList.push(property);
            }
        }
    }
    function transformColumnValueToCsvColumn(value: any) {
        if (value === null || value === undefined) {
            return '';
        }
        if (typeof value !== 'string') {
            value = value.toString();
        }
        if (value.includes(columnDelimiter) || value.includes(quoteChar) || value.includes(newline)) {
            return quoteChar + value.split(quoteChar).join(quoteChar + quoteChar) + quoteChar;
        }
        return value;
    }
    const lines: string[] = [
        columnNameList.map(columnName => transformColumnValueToCsvColumn(columnName)).join(columnDelimiter)
    ];
    for (const obj of array) {
        if (typeof obj === 'object') {
            const line = [];
            for (const property of columnNameList) {
                line.push(transformColumnValueToCsvColumn(obj[property]));
            }
            lines.push(line.join(columnDelimiter));
        }
    }
    return lines.join(newline);
}

example.md

Example of usage:

const str = arrayToCsvString([{a: 1, b: 2}, {b: 3, c: 4}]);
console.log(str);

Returns the string:

a,b,c
1,2,
,3,4