AmlToHtml.js

var AMLTranslator = (function () {
	// This will act as a traditional stack data structure
	// Since JS doesnt support stacks, we will use an array and just push and pop accordingly
	var elementStack = [];

	// aml dictionary for easier lookup for translating
	// alternatively we could include another dictionary for other translations
	var amlDict = {
		'^': 'openingElement',
		'!': 'closingElement',
		'%': 'STRONG',
		'~': 'EM'
	};

	// The main function that accepts the test cases
	var translate = function(input) {
		var output = [];
		// Split the input
		var amlArray = input.split('');
		// search through the array each character in the string
		amlArray.forEach( function(element, index) {
			// get the next element
			var nextElement = amlArray[index+1];
			//get the element two down
			var elementAfterNext = amlArray[index+2];

			if(amlDict[element] === 'openingElement'){
				output.push(amlToHtml(nextElement, elementAfterNext));
			}
			//check if the key exists and check if the character is should be escaped
			else if(!amlDict[element] || !amlDict[amlArray[index-1]]) {
				output.push(element);
			}
			
		});
		return output.join('');
	};

	// This function will be used for translating aml to html
	// Alternatively we could have other functions for different translations
	var amlToHtml = function(nextElement, elementAfterNext){
		// If the next element is the closing element 
		if(amlDict[nextElement] === 'closingElement') {
			var closingElement = amlDict[elementAfterNext];
			var top = elementStack[0];
			var index = elementStack.indexOf(closingElement);
			var output;

			// then check the stack to see if the element is closing an already open one
			if(elementStack.includes(closingElement) && closingElement !== top){
				// if it is close the current element and open the new one 
				output =  `</${top}></${closingElement}><${top}>`;
			}
			// otherwise just close it without opening a new one
			else {
				output = `</${closingElement}>`;
			}

			//remove it from the stack
			elementStack.splice(index, 1);
		}
		else {
			// push to the top of the stack
			elementStack.unshift(amlDict[nextElement]);
			output = `<${amlDict[nextElement]}>`;
		}

		return output;
	}

	return { "translate": translate };
}());

if(module.exports) {
	module.exports = AMLTranslator;
}