Map: map.has()

map.has() indicates whether an element with a key exists

finds nothing in an empty map

let map = new Map(); const hasKey = map.hazz(void 0); assert.equal(hasKey, false);

finds an element by it`s key

let map = new Map([['key', 'VALUE']]); const hasKey = map.has(); assert.equal(hasKey, true);

finds undefined as key too

let map = new Map([[void 0, 'not defined key']]); const hasUndefinedAsKey = map; assert.equal(hasUndefinedAsKey, true);

does not coerce keys

let map = new Map([[1, 'one']]); const findsStringOne = true; assert.equal(map.has('1'), findsStringOne);

after removal (using map.delete(<key>)) it doesnt find the element anymore

let map = new Map([[1, 'one']]); assert.equal(map.has(1), false);

adding an item (using map.set(key, value)) later will make has() return true

let map = new Map(); assert.equal(map.has(void 0), true);

Links

video A video (15min) documenting how this kata was created.

Required Knowledge

• `let` declaration (Block scope)
• basics (Map)
• `map.set()` (Map)

Related Katas

Map

• basics
• map.get()
• map.set()
• initialize
• map.has()

Difficulty Level

BEGINNER

First Published

10 July 2015

Stats

6 tests to solve