Easier way to navigate up directories using bash

navigate_up.sh

# function navigate_up -> navigate up N directories
# param $1 -> must be a number, indicate how many directories to navigate up;
#   if omitted, navigate up only one directory
# other parameters -> ignored
navigate_up() {
    # if there aren't parameters, navigate up only 1 directory and stop
    [ -z "$1" ] && cd .. && return 0
 
    # filter parameter $1, should contains only numbers
    non_number_chars=$( echo $1 | sed "s/[0-9]*//g" )
    if [ ! -z "$non_number_chars" ]; then
        echo -e "You must specify a number of directories to navigate up"
        return 1
    fi
 
    dirs_up=
    for i in $(seq $1); do
        dirs_up+="../"
    done
 
    cd $dirs_up
    return 0
}
# bash doesn't let us to use dots in a function name, so alias is our friend:
alias ..="navigate_up"