15. hide, show, toggle and isVisible

zz( '#t15-1' ).hide()
Must be hided
zz( '#t15-2' ).show()
Must be shown
'#t15-3' is visible: zz( '#t15-3' ).toggle()
Must be toggled
'#t15-4' is NOT visible: zz( '#t15-4' ).toggle()
Must be toggled
zz( '#t15-5' ).isVisible()
Is visible
zz( '#t15-6' ).isVisible()
Is NOT visible
display is inline:
zz( '#t15-7-2' ).hide();
zz( '#t15-7-2' ).show();
Span 1 Span 2 Span 3
'#t15-8' is visible, must be hide: zz( '#t15-8' ).toggle( false )
Must be toggled
'#t15-9' is visible, do not change: zz( '#t15-8' ).toggle( true )
Must be toggled
'#t15-10' is NOT visible, do not change: zz( '#t15-10' ).toggle( false )
Must be toggled
'#t15-11' is NOT visible, must be shown: zz( '#t15-11' ).toggle( true )
Must be toggled
zz( '#t15-12' ).hide()
Must not be changed
zz( '#t15-13' ).show()
Must not be changed
zz( '#t15-14' ).hide()
zz( '#t15-14' ).show()
Must not be changed