如何使用 object 密钥更新 javascript map 的值

Question

I have a map with an object as a key. For example: {date:"01/01/1990", idActiv:"4"}.

Then as a value, I have a string ("T" or "F") that represents True or False. My goal is to update that value, given a key.

var mapElem = new Map();

mapElem.set({date: "08/06/2020", idActiv: "1"}, "T");
mapElem.set({date: "18/06/2020", idActiv: "3"}, "T");

How I can update the map with object key {date: "08/06/2020", idActiv: "1"}?

If I do this:

mapElem.set({date: "08/06/2020", idActiv: "1"},"F"); 

I will have keyes repeated (Mozilla Firefox console):

mapElem.set({date: "08/06/2020", idActiv: "1"},"F");
Map(3)
​
size: 3
​
<entries>
​​
0: Object { date: "08/06/2020", idActiv: "1" } → "T"
​​
1: Object { date: "18/06/2020", idActiv: "3" } → "T"
​​
2: Object { date: "08/06/2020", idActiv: "1" } → "F"
​

Answer 1

You have to store objects as {date: "08/06/2020", idActiv: "1"} lone expression creates new instance somewhere

 const obj1 = {date: "08/06/2020", idActiv: "1"}; const obj2 = {date: "18/06/2020", idActiv: "3"} var mapElem = new Map(); mapElem.set(obj1, "T"); // mapElem.set(obj1.valueOf(), "T"); // equivalent mapElem.set(obj2, "T"); // mapElem.set(obj2.valueOf(), "T"); // equivalent mapElem.set(obj1, "F"); // mapElem.set(obj1.valueOf(), "F"); // equivalent console.log([...mapElem.entries()]);

Answer 2

Since, Object is a reference type, 2 Objects even with the same properties (basically 2 identical objects) are different, as they are 2 different references. The following should work as they are using the same Object (same reference) as a key in the map

var mapElem = new Map();

const key1 = {date: "08/06/2020", idActiv: "1"};
const key2 = {date: "18/06/2020", idActiv: "3"};

mapElem.set(key1, "T");
mapElem.set(key2, "T");

The same refernce key can be used later to update the value in the Map -

mapElem.set(key1,"F");

Alternatively, if the use case do no necessarliy require the keys to be object, you can serialize the object JSON.stringify(object) before using it as the key