Map.prototype.delete()

map.delete(key)

Returns: boolean · Updated March 13, 2026 · Map and Set

map delete remove

The delete() method removes a single entry from a Map by key. It returns true when the key existed and the entry was removed, or false when the key was not present. That boolean return value makes Map.prototype.delete() handy for cache invalidation, conditional cleanup, and other code paths where you want to know whether anything actually changed.

Syntax

map.delete(key)

Parameters

Parameter	Type	Description
key	any	The key to remove from the map

Return Value

Returns true if the key existed and was removed. Returns false if the key was not found.

Examples

Basic usage

const roles = new Map([
  ['alice', 'admin'],
  ['bob', 'editor'],
  ['charlie', 'viewer']
]);

console.log(roles.delete('bob'));
// true

console.log(roles.has('bob'));
// false

console.log(roles.size);
// 2

Deleting a missing key

const cache = new Map([['theme', 'dark']]);

console.log(cache.delete('language'));
// false

console.log(cache.size);
// 1

Conditional invalidation

const sessions = new Map([
  ['a1', { user: 'alice' }],
  ['b2', { user: 'bob' }]
]);

function invalidateSession(id) {
  if (sessions.delete(id)) {
    return `Session ${id} removed`;
  }

  return `Session ${id} was not active`;
}

console.log(invalidateSession('a1'));
// Session a1 removed