Swiped - Parsing error on app ready function

I want to slideto a specific slide using dmx swiper on app ready. Sometimes it works and sometimes it does not and I get and error.

This is my code for the app ready slideto. var_today is today’s day of the month returned as 5 or 6 or 31 for instance:

<body is="dmx-app" id="index" class="uk-height-viewport uk-flex uk-flex-column uk-flex-wrap-stretch" dmx-on:ready="swiperdays.slideTo(var_today.value)">

This is the error: