Serialise input as key-value pair string, eg. for human-readable logs.

kvp.js

/**
 * Serialise input as key-value pair string, eg. for human-readable logs.
 *
 * @param {any} body
 * @param {number} nest
 * @param {string} delimiter
 * @param {string} arrayDelimiter
 * @param {boolean} nested
 * @returns {string}
 */
toKeyValuePairString(body, nest = 2, delimiter = ' | ', arrayDelimiter = ', ', nested = false) {
    return isNull(body) ? 'null'
        : isUndefined(body) ? 'undefined'
            : Array.isArray(body)
                ? '[' + body.map(item => toKeyValuePairs(item, nest, delimiter, arrayDelimiter, true))
                            .join(arrayDelimiter) + ']'
                : typeof(body) === 'object'
                    ? (nested ? '{' : '')
                        + Object.entries(body).map(pair =>
                            nest > 0
                                ? [pair[0], toKeyValuePairs(pair[1], nest - 1, delimiter, arrayDelimiter, true)].join('=')
                                : [pair[0], pair[1]].join('=')).join(delimiter) + (nested ? '}' : '')
                    : String(body);
}

it('should serialise object to kvp', () => {
    const thing = {
        id: 1,
        name: 'fred',
        sibling: null,
        god: undefined,
        tags: [1, 2, 3],
        child: {name: 'bob'},
    };
    const actual = toKeyValuePairString(thing);
    expect(actual).toEqual('id=1 | name=fred | sibling=null | god=undefined | tags=[1, 2, 3] | child={name=bob}');
    expect(toKeyValuePairString('bob')).toEqual('bob');
    expect(toKeyValuePairString([1, 2, 3])).toEqual('[1, 2, 3]');
});