title: How can i calculate inside one input field
body: <p>So i have a form and in this form i have a field that i want to make simple maths in it for example if i type 25+25 my input becomes automatically 50 for now it only works if i use an integer after the operation symbol so 25+25 will be (275) 25+2 and then it will add the 5.
  Any idea how to fix this ?</p>
  <pre><code>&lt;input type=&quot;text&quot; name=&quot;input&quot; size=&quot;16&quot; id=&quot;answer&quot; on keyup =&quot; calc.input.value = eval(calc.input.value)&quot;&gt;
  </code></pre>