Postfix Evaluator.html

<script>

var input = "10 12 45 + -";

(function PostFix(input){
  
	var asArr = input.split(' ');
	var stack = [];
	
	asArr.forEach(function(ele,i){
	
		if (ele === "+") {
		
			var first = stack.pop();
			var second = stack.pop();
			stack.push(second+first);
		
		} else if (ele === "-") {
		
			var first = stack.pop();
			var second = stack.pop();
			stack.push(second-first);
		
		} else if (ele === "*") {
		
			var first = stack.pop();
			var second = stack.pop();
			stack.push(second*first);
		
		} else if (ele === "/") {
		
			var first = stack.pop();
			var second = stack.pop();
			stack.push(second/first);
		
		} else {
			stack.push(Number(ele));
		}
		
	});
	
	console.log(stack);
	
})(input);

</script>