title: Convert letter to number in JavaScript and calculator
body: <pre><code>  var letter = document.getElementById("in_text").value;
  </code></pre>
  
  <p>Get value From input box</p>
  
  <p>how to Convert input letter to number
  e.g A=1 B=2 C=3 ....and how to calculate = </p>
  
  <p>e.g: </p>
  
  <p>input: <code>demo</code><br>
  output: <code>37(4 + 5 + 13 + 15)</code></p>