title: how to populate form fields on the basis of other field's value in html using javascript
body: <p>I want to autopopulate a form element/field value instantly on the basis of another form field value using javascript.</p>
  
  <p>As shown in the figure, if a user fills the choice as "A" then the 'filled' field must automatically be filled with B without refreshing.</p>
  
  <p>Thanks in advance for help :)</p>
  
  <p><a href="https://i.stack.imgur.com/TCqkd.png" rel="nofollow noreferrer">Here is a screenshot</a> of how I want it to look: </p>