title: IIFE problem while creating a simple calculator
body: <p>I'm learning JS and wanted to practice for Functions and IIFE , below is the code i have made , at first i just created addition function , then i created subtraction function. while running the script it only showing the output of subtraction , hence i used IIFE . but still i don't know what should i do which will run both the functions. Please Suggest .</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>function showMessage() {
    console.log("A Simple Calculator")
  }
  
  showMessage();
  
  (function addition(x, y) {
    return x + y;
  
  })();
  
  addition(10, 11);
  
  (function subtraction(a, b) {
    return a - b;
  
  })();
  
  subtraction(25, 15);</code></pre>
  </div>
  </div>
  </p>