Baseline Widely available
The get()
method of Map
instances returns a specified element from this map. 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.
const map1 = new Map();
map1.set("bar", "foo");
console.log(map1.get("bar"));
// Expected output: "foo"
console.log(map1.get("baz"));
// Expected output: undefined
Syntax Parameters
key
The key of the element to return from the Map
object.
The element associated with the specified key, or undefined
if the key can't be found in the Map
object.
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);
myMap.get("bar").push("foo");
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
.
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