微信内公众号支付无需点击直接发起支付js

<script type="text/javascript">
function jsApiCall()
{
   WeixinJSBridge.invoke(
      'getBrandWCPayRequest',
      <?php echo $jsApiParameters; ?>,
      function(res){          
         WeixinJSBridge.log(res.err_msg);
         if(res.err_msg!='get_brand_wcpay_request:ok'){
            alert('支付取消.');
            history.back(-1);
         }
         window.location.href="<?php echo $return_url;?>";
      }
   );
}
function callpay()
{
   if (typeof WeixinJSBridge == "undefined"){
       if( document.addEventListener ){
           document.addEventListener('WeixinJSBridgeReady', jsApiCall, false);
       }else if (document.attachEvent){
           document.attachEvent('WeixinJSBridgeReady', jsApiCall); 
           document.attachEvent('onWeixinJSBridgeReady', jsApiCall);
       }
   }else{
       jsApiCall();
   }
}
callpay();
</script>