Navigate forward and backward in bash like a browser

navigate.sh

# functions for navigating forward and backward
NAVIGATION_FWD=()
NAVIGATION_BWD=()
navigate_forward () {
    if [ ${#NAVIGATION_FWD[@]} -gt 0 ]; then
        NAVIGATION_BWD+=("$(pwd)")
        cd "${NAVIGATION_FWD[${#NAVIGATION_FWD[@]}-1]}"
        unset NAVIGATION_FWD[${#NAVIGATION_FWD[@]}-1]
    fi
}
navigate_backward () {
    if [ ${#NAVIGATION_BWD[@]} -gt 0 ]; then
        NAVIGATION_FWD+=("$(pwd)")
        cd "${NAVIGATION_BWD[${#NAVIGATION_BWD[@]}-1]}"
        unset NAVIGATION_BWD[${#NAVIGATION_BWD[@]}-1]
    fi
}
nd () {
    NAVIGATION_BWD+=("$(pwd)")
    NAVIGATION_FWD=()
    cd "$@"
}