The get() method returns a specified element from a Map object. If the value that is associated to the provided key is an object, then you will get a reference to that object and any change made to that object will effectively modify it inside the Map object.

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The key of the element to return from the Map object.

Return value

The element associated with the specified key, or undefined if the key can't be found in the Map object.


Using get()

const myMap = new Map();
myMap.set('bar', 'foo');

console.log(myMap.get('bar')); // Returns "foo"
console.log(myMap.get('baz')); // Returns undefined

Using get() to retrieve a reference to an object

const arr = [];
const myMap = new Map();
myMap.set('bar', arr);


console.log(arr); // ["foo"]
console.log(myMap.get('bar')); // ["foo"]

Note that the map holding a reference to the original object effectively means the object cannot be garbage-collected, which may lead to unexpected memory issues. If you want the object stored in the map to have the same lifespan as the original one, consider using a WeakMap.


ECMAScript Language Specification
# sec-map.prototype.get

Browser compatibility

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See also