Pyramid

pyramid.js

// This require Node.js framework to complete the test case.

var pyramid = function (row, char, bg) {
	if (row < 1) {
		throw new Error("Row must be greater than 0.");
	}

	bg = bg || ' ';

	var lastRowNumChar = calculateNumChar(row - 1),
		numChar = 0,
		padding = 0,
		chars = '',
		tmpChars = '',
		currentRow = 0
	;
	for (; currentRow != row; ++currentRow) {
		// Process string to print from provided char argument.
		numChar = calculateNumChar(currentRow);
		tmpChars = repeatChar(char, numChar);

		// Then calculate padding string.
		numPadding = (lastRowNumChar - numChar) / 2;
		chars += padLeft(tmpChars, bg, numPadding) + "\n";
	}

	return chars;

	// Helper functions below here.

	function calculateNumChar(row) {
		return 2 * row + 1;
	}

	function padLeft (text, paddingChar, num) {
		paddingChar = paddingChar || ' ';

		return repeatChar(paddingChar, num) + text;
	}

	function repeatChar (char, num) {
		var str = '';

		for (; num !== 0; --num) {
			str += char;
		}

		return str;
	}
};

var assert = require('assert');

assert.throws(function () { pyramid(0, '#'); }, Error);
assert.equal(pyramid(1, "#").replace(/\s+$/, ''), "#");
assert.equal(pyramid(2, '#').replace(/\s+$/, ''), " #\n###");
assert.equal(pyramid(3, '#').replace(/\s+$/, ''), "  #\n ###\n#####");
assert.equal(pyramid(3, '#', '+').replace(/\s+$/, ''), "++#\n+###\n#####");