Js reference type as update pointer to other memory cell [duplicate]

Are there any strong reference and pointer mechanisms in javascript? For example now if I execute a code like this, the pointer that was referenced to USER and was added to MAP , will be lost. But I expect a behavior where when I assign an object, js understands that this pointer has an object in memory and it also changes the object in Map previously added.

let user = { age: 21 };
let cat = { age: 55 }

var m = new Map();
m.set(1, user);
user = cat;
cat.age = 77;