I'd like to start using ES6 Map instead of JS objects but I'm being held back because I can't figure out how to JSON.stringify()
a Map
. My keys are guaranteed to be strings and my values will always be listed. Do I really have to write a wrapper method to serialize?
Both JSON.stringify
and JSON.parse
support a second argument. replacer
and reviver
respectively. With replacer and reviver below it's possible to add support for native Map object, including deeply nested values
function replacer(key, value) {
if(value instanceof Map) {
return {
dataType: 'Map',
value: Array.from(value.entries()), // or with spread: value: [...value]
};
} else {
return value;
}
}
function reviver(key, value) {
if(typeof value === 'object' && value !== null) {
if (value.dataType === 'Map') {
return new Map(value.value);
}
}
return value;
}
Usage:
const originalValue = new Map([['a', 1]]);
const str = JSON.stringify(originalValue, replacer);
const newValue = JSON.parse(str, reviver);
console.log(originalValue, newValue);
Deep nesting with combination of Arrays, Objects and Maps
const originalValue = [
new Map([['a', {
b: {
c: new Map([['d', 'text']])
}
}]])
];
const str = JSON.stringify(originalValue, replacer);
const newValue = JSON.parse(str, reviver);
console.log(originalValue, newValue);