Undefined – The undefined means some variable is declared but the value of variable is not defined yet.
Object - Object means some variable is declared but the value of variable is not defined that is either function, object OR array.
You can easily be understanding in the below example in detail –
let emp; //The declaration of emp is hoisted but the value of emp is undefined.
console.log(emp); //The output is undefined
console.log(typeof(null)); // object
console.log(typeof(undefined)); // undefined