Do you have a select all option for Checkboxes?

I have a similar requirement with my form AuSim2.  On your demo, when I click Select All the form disappears and it displays <script type="text/javascript" src="//ying.jotform.com/jsform/21003710411431"></script>

can you help me set this up for my form?

We now have a widget that works exactly like a select all option. 

https://widgets.jotform.com/widget/select_all

Related guide: How-to-Add-a-Widget-to-your-Form

Give that a spin and let us know if you'd need more help.