Check if a variable exists in a list in Bash

Question

I am trying to write a script in bash that check the validity of a user input.
I want to match the input (say variable x) to a list of valid values.

what I have come up with at the moment is:

for item in $list
do
    if [ "$x" == "$item" ]; then
        echo "In the list"
        exit
    fi
done

My question is if there is a simpler way to do this,
something like a list.contains(x) for most programming languages.

Say list is:

list="11 22 33"

my code will echo the message only for those values since list is treated as an array and not a string, all the string manipulations will validate 1 while I would want it to fail.

Answer 1

[[ $list =~ (^|[[:space:]])$x($|[[:space:]]) ]] && echo 'yes' || echo 'no'

or create a function:

contains() {
    [[ $1 =~ (^|[[:space:]])$2($|[[:space:]]) ]] && exit(0) || exit(1)
}

to use it:

contains aList anItem
echo $? # 0： match, 1: failed