title: Woocommerce plus/minus quantity button changing value but not working actually
body: <p>I have created a plus/minus quantity button for woocommerce single product page.created a new quantity-input.php</p>
  
  <pre><code>&lt;?php
      if ( ! defined( 'ABSPATH' ) ) 
          exit; // Exit if accessed directly
  ?&gt;
  &lt;div class="quantity"&gt;
      &lt;input class="minus" type="button" value="-"&gt;
      &lt;input type="number" step="&lt;?php echo esc_attr( $step ); ?&gt;" &lt;?php if ( is_numeric( $min_value ) ) : ?&gt;min="&lt;?php echo esc_attr( $min_value ); ?&gt;"&lt;?php endif; ?&gt; &lt;?php if ( is_numeric( $max_value ) ) : ?&gt;max="&lt;?php echo esc_attr( $max_value ); ?&gt;"&lt;?php endif; ?&gt; name="&lt;?php echo esc_attr( $input_name ); ?&gt;" value="&lt;?php echo esc_attr( $input_value ); ?&gt;" title="&lt;?php _ex( 'Qty', 'Product quantity input tooltip', 'woocommerce' ) ?&gt;" class="input-text qty text" size="4" /&gt;
      &lt;input class="plus" type="button" value="+"&gt;
  &lt;/div&gt;
  </code></pre>
  
  <pre class="lang-js prettyprint-override"><code>$('.plus').on('click', function(e) {
      var val = parseInt($(this).prev('input').val());
      $(this).prev('input').attr( 'value', val+1 );
  });
  
  $('.minus').on('click', function(e) {
      var val = parseInt($(this).next('input').val());
      if (val !== 0) {
          $(this).next('input').val( val-1 );
      } 
  });
  </code></pre>
  
  <p>The above code changes the value of the text visually box but doesn't change the value in the code.As a result, woocommerce doesn't get any changes of quantity.On the other hand if I press up/down button of keyboard, changes of value is being got by woocommerce.I think it is happening because I have used <code>.val()</code> instead of <code>.attr()</code>, I changed to <code>attr()</code> many times but in vain.</p>