Use data from one textfield to populate other textfields in drupal 7 form I am new to drupal. I have a drupal form having fields Customer Name, Address and Phone. Is it possible to populate Name and Address Field automatically from database when the phone number is entered? 

I am using Drupal 7. 

Please help me and treat me as a beginner. Thank you...
Computed Field


  Computed Field is a very powerful field module that lets you add a
  custom "computed fields" to your content types. These computed
  fields are populated with values that you define via PHP code. You
  may draw on anything available to Drupal, including other fields, the
  current user, database tables, you name it. (Feeling the power yet? :)
  ) You can also choose whether to store your computed field values in
  the database with other content fields, or have them "calculated" on
  the fly during node views. (Although you should note that Views use
  requires database stored values.) This field is literally the Swiss
  Army knife of fields. So start cooking up your PHP based values!


OR

You can do it by using hook_form_alter then define copy_field_value.js create behavior:

(function($) {
  Drupal.behaviors.moduleNameCopyFieldValue = {
    attach: function (context, settings) {

      // Repeat this for all fields as needed
      $('#source', context).on('blur', function () { 
        // above you can use change instead of blur if element is not changed by another js
        if (!$('#destination').val() || 0 === $('#destination').val().length) {
          $('#destination').val($(this).val());
          // wrap line above in "if no value" like I did, or other condition you like
        }
      });
      // end of "repeat this"
    }
  };
})(jQuery);