title: How to add private variable to this Javascript object literal snippet?
body: <p>Found this at MDC but how if I'd wanted to add a private variable to the</p>
  
  <pre><code>var dataset = {
      tables:{
          customers:{
              cols:[ /*here*/ ],
              rows:[ /*here*/ ]
          },
          orders:{
              cols:[ /*here*/ ],
              rows:[ /*here*/ ]
          }
      },
      relations:{
          0:{
              parent:'customers', 
              child:'orders', 
              keyparent:'custid', 
              keychild:'orderid',
              onetomany:true
          }
      }
  }
  </code></pre>
  
  <p>The way I understand OOP in Javascript, I'd have access to dataset.tables.customers.cols[0] if such an item exists.<br>
  But if I wanted to place a private variable into customers, what would that look like?<br>
  Adding <code>var index = 0;</code> results in a runtime error.</p>