Fixing #83.

Author: blakeembrey

stack-machine/stack-machine.js

@@ -21,9 +21,9 @@ module.exports = function (S) {
   try {
     for (var i = 0; i < S.length; i++) {
       if (S[i] === '+') {
-        stack.push(addition.apply(null, stack.splice(-2)));
+        stack.push(addition.call(null, stack.pop(), stack.pop()));
       } else if (S[i] === '*') {
-        stack.push(multiply.apply(null, stack.splice(-2)));
+        stack.push(multiply.call(null, stack.pop(), stack.pop()));
       } else {
         stack.push(+S[i]);
       }
@@ -32,5 +32,5 @@ module.exports = function (S) {
     return -1;
   }
 
-  return stack.pop() || -1;
+  return stack.length ? stack.pop() : -1;
 }

test/javascript/stack-machine.js

@@ -1,16 +1,17 @@
 var stackMachine = require('../../stack-machine/stack-machine'),
     assert       = require('assert');
 
-describe('stackMachine', function () {
+describe('stack machine', function () {
   it('should correctly evaluate the two example problems', function () {
     assert.equal(stackMachine('13+62*7+*'), 76);
     assert.equal(stackMachine('11++'),      -1);
   });
 
   it('should return the top number from the stack', function() {
-    for(var i = 0; i < 10; i++)
+    for (var i = 0; i < 10; i++) {
       assert.equal(stackMachine(i.toString()), i,
         stackMachine(i.toString()) + ' == ' + i + '\n     Input: ' + i.toString());
+    }
     assert.equal(stackMachine('0123456789'),   9);
     assert.equal(stackMachine('123456*****0'), 0);
   });