Adding & Subtracting w/ function

Showing how to update numbers with same function

HTML

<form id="say-form" onsubmit="return false;" action="#">
    <input hidden type="text" id="said" value="1" size="3" autocomplete="off" />
    <input type="button" id="add" value="Add" />
    <input type="button" id="subtract" value="Subtract" />
</form><br />
<form id="say-form" onsubmit="return false;" action="#">
    <input hidden type="text" id="said" value="1" size="3" autocomplete="off" />
    <input type="button" id="add" value="Add" />
    <input type="button" id="subtract" value="Subtract" />
</form><br />
<br />
<div id="cart"></div>

JavaScript

// Declare VARIABLES and set them same time
var form     = document.getElementById( 'say-form' );
var add      = document.getElementById( 'add' );
var subtract = document.getElementById( 'subtract' );
var input    = document.getElementById( 'said' );
var cart     = document.getElementById( 'cart' );
var items    = 0;

var updateItems = function() {
    
  // set the HTML inside "cart"
  cart.innerHTML = "You have " + items + " items";
    
};

// "form" will now run a FUNCTION when user submits form
add.onclick = function() {
   
  items = items + parseInt( input.value );
    
  updateItems();
       
};


subtract.onclick = function() {
    
  items = items - parseInt( input.value );
    
  updateItems();
    
};