Question

Which of the following JavaScript statements can be used to access the last element of an array named myArray?

• A. myArray [myArray.length+1]
• B. myArray [myArray.length]
• C. myArray [myArray.length - 1]
• D. myArray [MyArray]

Hint:

In modern JavaScript, you can also use the newer .at() method to get the last element: myArray.at(-1) works just like myArray[myArray.length - 1].

Answer 1

The Correct Option is C

Step 1: Understanding Array Indexing:
JavaScript arrays use zero-based indexing. This means the first element of an array is at index 0, the second is at index 1, and so on.

Step 2: Linking Array Length to Last Index:
If an array contains $N$ elements, its .length property returns $N$. Because indexing starts at $0$, the indices of the array range from: $$0 \text{ to } (N - 1)$$ Therefore, the last element is always located at index: $$\text{Last Index} = \text{myArray.length} - 1$$

Step 3: Verification of Options:
Assume an array myArray = ["A", "B", "C"] with a length of $3$.
• (A) myArray[length+1]: Tries to access index $4$, which is empty/undefined.
• (B) myArray[length]: Tries to access index $3$, which is also undefined (one index past the last valid element).
• (C) myArray[length-1]: Accesses index $2$ ("C"), successfully retrieving the last element.
• (D) myArray[MyArray]: Passes an object reference as an index, which is invalid.