title: Press button to "Bold" & press again to "Unbold"
body: <p>I am new to javascript. I want to make a button in html using javascript. When user try to press the button
  the specific &lt;#id> is going to be "Bold" and press again to "Unbold". </p>
  
  <p>How can I do this ? please refer any helping material.
  Thanks !</p>