bash - Why is 'if' statement not working? -

i don't seem understand why if statement isn't working. reason doesn't work , hope can give me advice!

function startup {          #budate bevat het jaartal,maand en dag van nu.     budate=`date +%y%m%d`         #maakt directory aan in backup map met datum als naam     mkdir backupmap/$budate }  function getday {  dow=$(date +%u) backuptype=""       case $dow in         '1' )             #maandag             backuptype="inc"             ;;         '2' )             #dinsdag             backuptype="inc"             ;;         '3' )             #woensdag             backuptype="inc"             ;;         '4' )             #donderdag             backuptype="inc"             ;;         '5' )             #vrijdag             backuptype="full"             echo "got date"             ;;         '6' )             #zaterdag             backuptype="inc"             ;;         '7' )             #zondag             backuptype="full"             ;;     esac }  function copyfull {     cd nfs/backup/servers     files=(*)         ((x=0; x<${#files[@]}; x++))                     cd ${files[$x]}         cd full         rsync `ls -tp | grep -v / | head -n 2` ../../../../../backupmap/$budate         cd ../../     done }  function copyinc {     cd nfs/backup/servers     files=(*)         ((x=0; x<${#files[@]}; x++))                     cd ${files[$x]}         cd incremental         rsync `ls -tp | grep -v / | head -n 4` ../../../../../backupmap/$budate         cd ../../     done }  function fullorinc ($backuptype){         if [[ $backuptype=="inc" ]];         copyinc     elif [[ $backuptype=="full" ]];         copyfull     elif [[ $backuptype=="" ]];         echo "couldn't current date."     fi  } startup getday 

the spaces around == in [[ ... ]] not optional. without them, condition understood as

[[ -n "$backuptype==" ]]