<lightning:combobox aura:id="filterCaseType" label = "{!$Label.c.CPL_Event_Type}" name="caseTypes" placeholder="Case Type" options="{!v.caseEventTypeOptions }" onchange="{!c.filterCasesByType }"/>
caseEventTypeOptions --> Is list of Key value pair
now values are Sunday, Monday, Tuesday, Wednesday.....Saturday.
Now when page loads i want Tuesday to be selected by default. How can i achieve this in aura:lightning cmp on java script side.