How can I create new map and merge with first

Question

var myMap = {
17035: "box",
93133: "box",
97872: "bag",
};

const code = "packet";
const listOfFirst = [92327, 91278];

var newMap = new Map();

listOfFirst.forEach(item => newMap.set(item, code));

const resullt = new Map([
...myMap,
...newMap,
]);

I try to get:
const resullt = {
17035: 'box',
93133: 'box',
97872: 'bag',
92327: 'packet',
91278: 'packet'
}

Answer 1

const resullt = new Map([
...myMap,
...newMap,
]);

The Map constructor accepts an array or array-like collection of key-value pairs.

With snippet as-is, you are trying to pass the constructor a plain object and a Map object.

You can convert the myMap and newMap to an iterator of key-value pairs.

By doing so you will then be able to use the spread operator to pass them to the Map constructor.

should be
const resullt = new Map([
...Object.entries(myMap),
...newMap.entries(),
]);

Answer 2

You can try a less than ideal time complexity solution where you just create a new map, then go over the contents of each map you want to add with a loop, and add individually to the new map.

Though you're most likely going to use a nested loop so it'll have terrible time complexity. Probably like log n².

Answer 3

It does not mater i try modify myMap, but I can not, it does not work. Any others solutions?

Answer 4

var myMap

if you want 'var resullt'

Answer 5

I found solution:

listOfFirst.forEach(item => {
myMap = {
...myMap,
[item]: code
};
});

console.log('myMap = ', myMap);

Answer 6

That's because you have it as a constant. Remember, constants cannot be changed.

edit: I got this mixed up with Java, sorry about that.