A Stack-Based Calculator

This JavaScript Reference section displays the code for an example program that shows how to create a stack-based calculator in JavaScript.

StackBasedCalculator.html

<!DOCTYPE html>
<html>
<head>
    <title>XoaX.net's Javascript</title>
    <script type="text/javascript" src="StackBasedCalculator.js"></script>
</head>
<body onload="fnInitialization()">
    <p id="idAnswer"></p>
</body>
</html>

StackBasedCalculator.js

// The Link Constructor
function CLink(qData) {
  this.mqData = qData;
  this.mqpNext = null;
}

// The LinkedList Constructor
function CLinkedList() {
  this.mqpHead = null;
  this.mfnInsertAtHead = function(qData) {
    var qpOldHead = this.mqpHead;
    this.mqpHead = new CLink(qData);
    this.mqpHead.mqpNext = qpOldHead;
  }
  this.mfnRemoveAtHead = function() {
    this.mqpHead = this.mqpHead.mqpNext;
  }
  this.mfnIsEmpty = function() {
    return (this.mqpHead == null);
  }
}

// The Stack Constructor
function CStack() {
  this.mqList = new CLinkedList();
  this.mfnPush = function(qData) {
    this.mqList.mfnInsertAtHead(qData);
  }
  this.mfnPop = function() {
	var qPopped = this.mqList.mqpHead;
    this.mqList.mfnRemoveAtHead();
    return qPopped.mqData;
  }
  this.mfnIsEmpty = function() {
    return this.mqList.mfnIsEmpty();
  }
}

function fnInitialization() {
	// The expression must have parentheses around each operation
	// Each number must be a single digit and positive.
	var sExpression = "((((3*4)+(5*2))/5)+(3*2))";

    var qNumberStack = new CStack();
    var qOperatorStack = new CStack();
    var qpPrint = document.getElementById("idAnswer");

    for (var sCurrChar of sExpression) {
		if (sCurrChar == '(') { // Check for a left parenthesis
			 // We do not need to do anything in this case
		} else if (sCurrChar == ')') { // Check for a right parenthesis
			// Get the numbers in reverse order
			var dY = Number(qNumberStack.mfnPop());
			var dX = Number(qNumberStack.mfnPop());
			// Get the operation, decipher, and calculate the value.
			sCurrChar = qOperatorStack.mfnPop();
			var dZ = 0.0
			switch (sCurrChar) {
				case '+': {
					dZ = (dX + dY);
					break;
				}
				case '-': {
					dZ = (dX - dY);
					break;
				}
				case '*': {
					dZ = (dX * dY);
					break;
				}
				case '/': {
					dZ = (dX / dY);
					break;
				}
			}
			qNumberStack.mfnPush(dZ);
		} else if ((sCurrChar == '+') || (sCurrChar == '-') ||
			(sCurrChar == '*') || (sCurrChar == '/')) { // Check for an operation
			// Push the operator value as a character onto the operator stack
			qOperatorStack.mfnPush(sCurrChar);
		} else if (sCurrChar >= '0' && sCurrChar <= '9') { // Check for a numeric digit
			// Push the character value as a number onto the number stack
			qNumberStack.mfnPush(sCurrChar);
		}
	}

	qpPrint.innerHTML = sExpression + " = " + Number(qNumberStack.mfnPop()) + "<br />";
}

Core JavaScript

A Stack-Based Calculator

StackBasedCalculator.html

StackBasedCalculator.js

Output