JSON stringifier that handles ES6 Maps

map2json.js

// Optional: If any dependency is overriding Map's toJSON function,
// you might want to reset it.
// Why? See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#toJSON()_behavior
delete Map.prototype.toJSON;

function customStringifier(key, value) {
    if (value instanceof Map) {
        // Convert Maps to JSON objects.
        let obj = Object.create(null);
        for (let [k, v] of value) {
            obj[k] = v;
        }
        return obj;
    } else {
        return value;
    }
}

const fixture = {
    "a": 1,
    "b": "c",
    "d": true,
    "e": new Map([["lol", "haha"], ["zero", 123], ["yes", false]]),
};

console.log(JSON.stringify(fixture, customStringifier));