JS Practice — Built-in Objects

Array.prototype.join() — custom separator

📖 Usage Example

const nums = [1, 2, 3]
nums.join(' - ')  // → '1 - 2 - 3'
nums.join('')     // → '123'

Pass any string as the separator to join() to control how elements are delimited.

Array.prototype.join() — any separator

join() accepts any string as the separator, including empty string, spaces, or multi-character strings.

Challenge: Implement joinWith(arr, sep) that joins the array using the given separator.

joinWith(['a', 'b', 'c'], '-') // → 'a-b-c'
joinWith(['a', 'b', 'c'], '')  // → 'abc'

💡 Hints (2)

• `join('')` concatenates all elements with no separator between them.
• The separator only appears *between* elements, not before the first or after the last.