a JSON.stringify replacer that prevents from circular structures & un-stringify-able properties

safeJsonReplacer.js

/**
 * Creates a formatter for JSON.stringify that prevents from circular structures and not stringify-able values
 */
function safeJsonReplacer() {
    const seen = new Set();

    return (key, val) => {
        // prevent from circular structures
        if (typeof val === 'object' && val !== null) {
            if (seen.has(val)) return;
            seen.add(val);
        }

        let formattedVal;
        if (val && [String, Number, Array, Object].includes(val.constructor)) { // return as-is if it is a safe value
            formattedVal = val;
        } else { // try to format if it is a dangerous value
            try {
                formattedVal = val.toString();
            } catch (e) {
                formattedVal = undefined;
            }
        }

        return formattedVal;
    };
}


console.log(JSON.stringify('string', safeJsonReplacer(), 2))
console.log(JSON.stringify(2, safeJsonReplacer(), 2))
console.log(JSON.stringify(["coucou", 1, 2, null, undefined], safeJsonReplacer(), 2))
console.log(JSON.stringify(global, safeJsonReplacer(), 2))