বিদেশে কোথায় প্রথম পাকিস্তানের ডেপুটি হাইকমিশন অফিসে বাংলাদেশের পতাকা উওোলন করা হয়?

Question Overview:

Analyze the following code snippet and identify the correct output from the given options.

Options:

    
• A) 3 4
    
• B) 4 4
    
• C) 3 3
    
• D) TypeError: Assignment to constant variable

Correct Answer: B) 4 4

Detailed Explanation:

In JavaScript, non-primitive data types such as Arrays and Objects are stored by reference rather than by value.

    
• When let b = a; is executed, variable b does not create an independent copy of the array. Instead, it receives a reference pointing to the same memory location as a.
    
• When b.push(4); is called, it mutates the underlying array in place.
    
• Since both a and b reference the identical array instance, any modification made through b is immediately reflected in a.
    
• Therefore, both a.length and b.length evaluate to 4.

Key Takeaway:

To avoid mutating the original array when assigning it to another variable, use shallow copying techniques such as the spread operator (let b = [...a];) or Array.prototype.slice().