title: Javascript increment a value
body: <p>I have tried and failed trying to get this to work so time to ask the experts.</p>
  
  <p>I've got the following HTML:</p>
  
  <pre><code>&lt;input type="button" value="-" class="minus"&gt;
  &lt;input type="number" value="20" class="input-text"&gt;
  &lt;input type="button" value="+" class="plus"&gt;
  
  &lt;div class="newprice"&gt;
      20
  &lt;/div&gt;
  </code></pre>
  
  <p>Using javascript (jQuery specific is fine) I need to be able to have it so that when someone clicks the plus button, the number inside the .newprice div gets incremented by 20. Likewise when they hit the minus button the number gets decreased by 20.</p>
  
  <p>Also the same goes for if they use the little up/down arrows on the .input-text field.</p>
  
  <p>Or if they type in a value instead of using any of the buttons, then the number in the .input-text div changes accordingly (if someone typed in 3, the .input-text number would change to 60).</p>
  
  <p>PS: if it's easier the .newprice div can be an text field instead. Whatever works.</p>
  
  <p>[To put this all into context, basically its part of a shopping cart but I am trying to show the user how much they will be paying for the product when they enter a quantity. For example, the product costs $20, and if they want 3 of them they will be able to see straight away (before adding to their cart) that this is going to cost them $60.]</p>
  
  <p>I hope I explained it properly.</p>
  
  <p>Thanks in advance.</p>