Shell script to compile javascript through Google Closure

compile-closure.sh

#!/bin/sh

usage(){
	echo "Usage: $0 inputfile.js closurecompiledfile.js"
	exit 1
}

is_file_exits(){
	local f="$1"
	[[ -f "$f" ]] && return 0 || return 1
}

[[ $# -eq 0 ]] && usage

if ( is_file_exits "$1" )
then
 java -jar ~/src/javascript/closure-compiler-v20170218.jar --js $1 --js_output_file $2
else
 echo "File not found"
fi