Javascript RPN Calculator

js

// JSRPN - a simple console display javaScript RPN calculator
// by Lars Johnson and Paul Gaston Gouron

var RPN = function(string){

  var poppush = function () {
          stack.pop()
          stack.pop()
          stack.push(value)
      }

  var input = string.split(" ");
  var stack = []
  var value = 0

  for (var s = 0; s < input.length; s++) {

    if (isNaN(input[s]) === false) {      // Equals Number
        stack.push(input[s]);             // Push onto stack
    }
    else {                                // ELSE do math

      var first = Number(stack[stack.length-1])
      var second = Number(stack[stack.length-2])

      switch (input[s]) {
        case "+":
          var value = first + second
          poppush()
          break

          case "-":
          var value = first - second
          poppush()
          break

          case "*":
          var value = first * second
          poppush()
          break

          case "/":
          var value = first / second
          poppush()
          break
      }
    }
  }
  return parseInt(stack)
}

// Test
console.log(RPN("70 10 4 + 5 * -"))