Question

Why a referenced object is not set to null when parent object is set to null in JavaScript?

var objA = { 1 : "hello" };
var objB = objA;
objA = null;

console.log(objB);  // { 1 : "hello" }

Why objB is not set to null? How object referencing works here?

Answer 1

Variables never “contain” objects, they simply contain a reference to an object.

var objB = objA; simply copies the reference stored in objA, making them point to the same object. When objA is set to null, it means that it no longer points to anything. However, objB still contains a reference to the object.