I got this recursion question during an interview and totally blew it. I forgot recursion existed, and my implementation didn't go smoothly. Here's another try.

recursive-star-triangle.js

/**
 * I got this recursion question during an interview and totally blew it. I
 * forgot recursion existed, and my implementation didn't go smoothly. Here's
 * another try.
 *
 * Question: Print a triangle of stars without using any loops, iteration, etc.
 *
 * Input: n = 3
 * Output:	*
 *		**
 *		***
 */

const triangle = getStarTriangle(3);

console.log(triangle);

function getStarTriangle(height, _currentRow = 0, _currentColumn = 0, _currentString = '')
{
	// Early exit condition, height may be undefined or 0.
	if (!height) return _currentString;

	// Recursion end condition.
	if (_currentRow == height) return _currentString;

	// A) Add star to row
	if (_currentColumn <= _currentRow) {
		_currentString += '*';
		return getStarTriangle(height, _currentRow, ++_currentColumn, _currentString);
	}

	// B) Create a new row
	if (_currentColumn > _currentRow) {
		_currentString += '\n';
		return getStarTriangle(height, ++_currentRow, 0, _currentString);
	}
}