code to add to cart by javascript
// Appends the required hidden values to PayPal's form before submitting
populatePayPalForm: function() {
var self = this;
if( self.$paypalForm.length ) {
var $form = self.$paypalForm;
var cart = self._toJSONObject( self.storage.getItem( self.cartName ) );
var shipping = self.storage.getItem( self.shippingRates );
var numShipping = self._convertString( shipping );
var cartItems = cart.items;
var singShipping = Math.floor( numShipping / cartItems.length );
$form.attr( "action", self.paypalURL );
$form.find( "input[name='business']" ).val( self.paypalBusinessEmail );
$form.find( "input[name='currency_code']" ).val( self.paypalCurrency );
for( var i = 0; i < cartItems.length; ++i ) {
var cartItem = cartItems[i];
var n = i + 1;
var name = cartItem.product;
var price = cartItem.price;
var qty = cartItem.qty;
$( "<div/>" ).html( "<input type='hidden' name='quantity_" + n + "' value='" + qty + "'/>" ).
insertBefore( "#paypal-btn" );
$( "<div/>" ).html( "<input type='hidden' name='item_name_" + n + "' value='" + name + "'/>" ).
insertBefore( "#paypal-btn" );
$( "<div/>" ).html( "<input type='hidden' name='item_number_" + n + "' value='SKU " + name + "'/>" ).
insertBefore( "#paypal-btn" );
$( "<div/>" ).html( "<input type='hidden' name='amount_" + n + "' value='" + self._formatNumber( price, 2 ) + "'/>" ).
insertBefore( "#paypal-btn" );
$( "<div/>" ).html( "<input type='hidden' name='shipping_" + n + "' value='" + self._formatNumber( singShipping, 2 ) + "'/>" ).
insertBefore( "#paypal-btn" );
}
}
}