sqmicro-connection/test/to-json.js

Connection abstraction for SQ Micro.

/**
 * Transform an oblect to JSON
 * @param {*} obj the object.
 * @param {number} [num=2] padding size.
 * @param {string|function} [circular] placeholder for circular references. A function
 * takes the first key under which the object was seen and returns the string,
 * which replaces the value.
 * @returns {string} json
 */
module.exports = function toJson(obj, num = 2, circular = defaultCircularPlaceholder) {
    let cache = [];
    if (typeof circularPlaceholder === 'string') {
        let placeholder = circular;
        circular = () => placeholder;
    }
    
    return JSON.stringify(obj, blockCirculars.bind(null, circular, cache, ), num);
};

function blockCirculars(circular, cache, key, value) {
    // block internals
    if (key.endsWith('$')) {
        return `[${key}]`;
    }

    // block circulars
    if (typeof value === 'object' && value !== null) {
        let cached = cache.find(item => item.value === value);
        if (cached) {
            return circular(cached.key);
        }
        cache.push({ key, value });
    }

    return value;
}

function defaultCircularPlaceholder(key) {
    return `[Circular ${key}]`;
}