Unable to delete map entries using map.delete() function

Question

I'm trying to delete the entry with key '1' in the map. Can anyone tell me why is map.delete(1) returning false and the entry is not being deleted.

let nums = [1,1,1,2,2,3]
let map = new Map();
    for (let num of nums) {
        if (num in map) {
            map[num]++;
        } else {
            map[num] = 1;
        }
    }
    console.log(map) // Map(0) { '1': 3, '2': 2, '3': 1, '4': 3 }
    console.log(map.delete(1)); // false
    console.log(map) // Map(0) { '1': 3, '2': 2, '3': 1, '4': 3 }

The code you posted does not create any 4 keys since there are no 4 values in your nums array. Please provide a minimal reproducible example. — Bergi
– Bergi, Commented Sep 10, 2022 at 4:30

Bergi · Accepted Answer · 2022-09-10 04:35:52Z

1

You need to use map.get() and map.set() instead of bracket syntax. Assigning properties to a map object doesn't actually use the Map, and is why map.delete() does nothing.

Either use a Map:

const map = new Map();
for (let num of nums) {
    if (map.has(num)) {
        map.set(num, map.get(num)+1);
    } else {
        map.set(num, 1);
    }
}
map.delete(1);

Or (ab)use an object as a collection:

const map = Object.create(null);
for (let num of nums) {
    if (num in map) {
        map[num]++;
    } else {
        map[num] = 1;
    }
}
delete map[1];

answered Sep 10, 2022 at 4:35

Bergi

671k162 gold badges1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sakil · Accepted Answer · 2022-09-10 04:37:14Z

0

let nums = [1,1,1,2,2,3, 4]
let map = new Map();
for (let num of nums) {
    if (num in map) {
        map.set(num, map.get(num)++);
    } else {
        map.set(num, 1)
    }
}
console.log(map)
console.log(map.delete(1))
console.log(map)

answered Sep 10, 2022 at 4:37

Sakil

6525 silver badges8 bronze badges

Collectives™ on Stack Overflow

Unable to delete map entries using map.delete() function

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related