Determine if a function exists in bash

fn_exists()
{
    type $1 | grep -q 'shell function'
}

batzel@batzel-laptop:~$ type foo
bash: type: foo: not found
batzel@batzel-laptop:~$ type ls
ls is aliased to `ls --color=auto'
batzel@batzel-laptop:~$ which type
batzel@batzel-laptop:~$ type type
type is a shell builtin

$ g() { return; }
$ declare -f g > /dev/null; echo $?
0
$ declare -f j > /dev/null; echo $?
1

test_declare () {
    a () { echo 'a' ;}

    declare -f a > /dev/null
}

test_type () {
    a () { echo 'a' ;}
    type a | grep -q 'is a function'
}

echo 'declare'
time for i in $(seq 1 1000); do test_declare; done
echo 'type'
time for i in $(seq 1 100); do test_type; done

real    0m0.064s
user    0m0.040s
sys     0m0.020s
type

real    0m2.769s
user    0m1.620s
sys     0m1.130s

fn_exists()
{
    type $1 2>/dev/null | grep -q 'is a function'
}

fn_exists test_function
if [ $? -eq 0 ]; then
    echo 'Function exists!'
else
    echo 'Function does not exist...'
fi

test_function () {
        ! type -f $1 >/dev/null 2>&1 && type -t $1 >/dev/null 2>&1
}