thow error instead of string error message

Author: k88manish

src/_DataStructures_/Stack/postfix-expression-evaluation/index.js

@@ -13,7 +13,7 @@ function evaluatePostfixExpression(expression) {
   expression = expression.trim();
 
   if (expression.length === 0 || expression.length === 1) {
-    return ERROR_STRING;
+    throw new Error(ERROR_STRING);
   }
 
   const s = new Stack();
@@ -52,7 +52,7 @@ function evaluatePostfixExpression(expression) {
   if (s.isEmpty()) {
     return result;
   }
-  return ERROR_STRING;
+  throw new Error(ERROR_STRING);
 }
 
 module.exports = {

src/_DataStructures_/Stack/postfix-expression-evaluation/postfix-expression-evaluation.test.js

@@ -56,8 +56,7 @@ describe('Postfix expression evaluation', () => {
   describe('should throw error on invalid expressions', () => {
     const invalidExpressions = ['12', '1', '+', '1+2', '+12'];
     test.each(invalidExpressions)('running for %p', (expression) => {
-      const result = evaluatePostfixExpression(expression);
-      expect(result).toEqual(ERROR_STRING);
+      expect(() => evaluatePostfixExpression(expression)).toThrow(ERROR_STRING);
     });
   });
 });