Explanation of some terms used in this article:

Any type of Map: means that the key of the Map object can be of any JavaScript type;
String Map: The keys of the Map object are all JavaScript Strings;
Binary pair: an array object with one and only two elements, such as [true,7];
Binary pair Array: An array object, each element of which is a binary pair.

Convert between any type of Map and JSON using binary Array

Conversion between Map and Array of Binary Pairs

Use the spread operator to convert a Map to an Array of binary pairs:

> let myMap = new Map().set(true, 7).set({foo: 3}, ['abc']);
undefined
> [...myMap]
[ [ true, 7 ], [ { foo: 3 }, [ 'abc' ] ] ]
>

Convert an Array of binary pairs into a Map:

> new Map([[true, 7], [{foo: 3}, ['abc']]])
Map {true => 7, Object {foo: 3} => ['abc']}

Conversion between Map and JSON string

Tool method:

function mapToJson(map) {
    return JSON.stringify([...map]);
}
function jsonToMap(jsonStr) {
    return new Map(JSON.parse(jsonStr));
}

Demo:

> let myMap = new Map().set(true, 7).set({foo: 3}, ['abc']);
undefined
> mapToJson(myMap)
'[[true,7],[{"foo":3},["abc"]]]'
> jsonToMap('[[true,7],[{"foo":3},["abc"]]]')
Map { true => 7, { foo: 3 } => [ 'abc' ] }

Convert between String Map and JSON using Object

Conversion between String Map and Object

Tool method:

function strMapToObj(strMap) {
    let obj = Object.create(null);
    for (let [k,v] of strMap) {
        obj[k] = v;
    }
    return obj;
}
function objToStrMap(obj) {
    let strMap = new Map();
    for (let k of Object.keys(obj)) {
        strMap.set(k, obj[k]);
    }
    return strMap;
}

Example demo:

> let myMap = new Map().set('yes', true).set('no', false);
> strMapToObj(myMap)
{ yes: true, no: false }
> objToStrMap({yes: true, no: false})
[ [ 'yes', true ], [ 'no', false ] ]

Conversion between String Map and JSON String

Tool method :

function strMapToJson(strMap) {
    return JSON.stringify(strMapToObj(strMap));
}
function jsonToStrMap(jsonStr) {
    return objToStrMap(JSON.parse(jsonStr));
}

Example demo:

> let myMap = new Map().set('yes', true).set('no', false);
> strMapToJson(myMap)
'{"yes":true,"no":false}'
> jsonToStrMap('{"yes":true,"no":false}');
Map {'yes' => true, 'no' => false}

Reference article

Converting ES6 Maps to and from JSON

This article is mainly based on the translation of this article.

Conversion between ES6 Map and Object/JSON String