ruby on rails - who changed the value of "params[:tab]"? -

in 1 erb file called x.html.erb, confused following little snippet code:

  <% params[:tab] |= "excursion" %>   <% availablemodels.each |modelname| %>     <% if modelname == "excursion" %>       <li class="<%= params[:tab]=='excursions' ? 'active':''%>">         <a id="excursions_tab" href="#tabexcursions" data-toggle="tab"> excursions         </a>       </li>     <% elsif modelname == "workshop" %>       <li class="<%= params[:tab]=='workshops' ? 'active':''%>">         <a id="workshops_tab" href="#tabworkshops" data-toggle="tab">workshop         </a>       </li>     <% end %> 

i found can not figure out how params[:tab] changed such params[:tab] = 'excursions'to params[:tab] = 'workshops', or vice versa, or said changes value of params[:tab] when toggle 1 tab excursion or workshop corresponding html:

<li class="active">    <div id="tab_excursions"> ...</div> </li> <li class>    <div id="tab_resources"> ... </div> </li> 

or

<li class>     <div id="tab_excursions"> ...</div> </li> <li class="active">    <div id="tab_resources"> ... </div> </li> 

for finding answer, tried change params[:tab] params[:tabx] , found worked fine. , <%= params[:tab]=='excursions' ? 'active':''%>, must relative 1 rails's magic?

the params[:tab] not change after created. part of rails stub performs logic on page load assist creating markup. way can guarantee params[:tab] hash has been defined current code at,

params[:tab] |= "excursion" 

|= assigns params[:tab] "excursion" if has not been set. current view params[:tab] equal "excursion". if either "excursion" or "workshop" show active on page load hash being set earlier snippet.

what have in elements data-toggle attribute groups 2 items under same parent node (i believe). bootstrap has javascript function within listens click on either of elements , toggles between 2 accordingly.

in short, bootstrap, js functionality. check out : http://getbootstrap.com/2.3.2/javascript.html#tabs, toggleable tabs

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determining tab set active based on params[:tab] value. after that, whichever tab click on set active bootstraps js , css , describable link provided