Let’s carefully analyze your code step by step:

<script>
    const emp = {name:'Suresh'}
    document.write(emp.name);

    emp = {name:'Ravi'}
    document.write('<br>'+emp.name)

    emp.name = 'Ravi'
    document.write('<br>'+emp.name)
</script>

Step 1: Declaration

const emp = { name: 'Suresh' };

• Here emp is declared as a constant reference.

• It holds a reference (a pointer) to the object { name: 'Suresh' }.

• Important: const means you cannot reassign emp to point to another object, but you can change the properties of the object.

Step 2: First Output

document.write(emp.name);

• Prints Suresh.

Step 3: Reassignment Attempt

emp = { name: 'Ravi' };

• ❌ This line will throw an error:
  Uncaught TypeError: Assignment to constant variable.

• Because emp is a const — you cannot assign a new object to it.

👉 As soon as this error happens, the script stops execution, so the next lines will not run.

Step 4: Property Update (if reassignment wasn’t there)

If instead of reassigning, you only updated the property like this:

emp.name = 'Ravi';
document.write('<br>'+emp.name);

• This works ✅ because you’re not changing the reference, only the internal property.

• Output would be:

Suresh
Ravi

Final Behavior of Your Code

• It prints:

Suresh

• Then throws an error at emp = {name:'Ravi'} and stops.

✨ Key Takeaway:

• const protects the reference (you can’t reassign it).

• But you can still change the contents (object properties).

👉 Do you want me to rewrite your code correctly so it prints

Suresh
Ravi

without any error?

Best Practice Recommendation:

• • Default to const: Use it by default for every variable. Its immutability makes code easier to reason about.

  • Use let for mutability: If you need to reassign a variable (e.g., a loop counter), use let.

  • Avoid var: There is almost no need to use var in modern ES6+ code. Its function-scoping behavior is more error-prone. Its use should be considered a legacy pattern.