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Map: map.has()

Indicates whether an element with a key exists.

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);


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First Published

10 July 2015


6 tests to solve