change file name extension in batch

changeExtension

#!/bin/bash
directoryName="$1"
extension="$2"

regex='.+'
if ! [[ $extension =~ $regex ]]; then
	echo "Usage: changeExtension directory newExtension";
	exit 1;
fi

if [[ -d $directoryName ]]; then

	FILES=$directoryName/*

	for file in $FILES
	do
		if [[ -d $file ]] ; then 
			continue	
		fi

		filename=$(basename "$file")
		oriExtentsion="${filename##*.}"
		filename="${filename%.*}"
		newFileName=$directoryName/$filename.$extension
		mv $file $newFileName
	done	

elif [[ -f $directoryName ]]; then

	echo "if file"

	filename=$(basename "$directoryName")
	oriExtentsion="${filename##*.}"
	filename="${filename%.*}"
	newFileName=$filename.$extension

	mv $directoryName $newFileName

fi