Using Javascript for Eval | AjaxAddOrderItem | Adding multiple parts to Cart

I ran into this problem in the past and realized, it's hard to remember the eval function and without that you could end up spending a lot of time, trying to figure out passing multiple params with dynamic values. (partNumber_1, quanitty_1...partNumber_2, quantity_2).

eval() evaluates the expression in the argument. If the argument is one or more JavaScript statements, eval() executes the statements.
E.g. service code.

    var renderCtx = wc.render.getContextById("AjaxAddToCartContext");
     //setting context properties  
    renderCtx.properties['partNumber'] = partNumber;
    renderCtx.properties['quantity'] = quantity;

     eval("params.partNumber_" + counter + "='"+partNumber+ "';");
     eval("params.quantity_" + counter + "="+quantity+ ";");
    //invoke the AJAX service for orderitem add (Cart Service)
     wc.service.getServiceById("AjaxAddOrderItem").formId = orderFormId;
     wc.service.invoke("AjaxAddOrderItem", params);