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

Jawwad Rizvi 0
Viewed 26

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 }
dictionary arrays javascript
2 Answers

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];
Bergi0 
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)
Sakil0
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