What is the recommended way to get nmap on OSX?

Can I just use apt-get, or should I use some Mac tool?

First Option

Nmap's Official Website

• Download the latest official installer here:
  https://nmap.org/download.html#macosx

• Check this out for additional information:
  https://nmap.org/book/inst-macosx.html

• Alternative versions can be found here:
  https://nmap.org/dist/

Second Option

Homebrew Package Manager

• Install Homebrew

  $ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
  

• Install Nmap

  $ brew install nmap
  

• Optional

  $ brew search nmap
  $ brew info nmap
  

Third Option

MacPorts Package Manager

• Install MacPorts

  $ bash -c "$(curl -fsSL https://raw.githubusercontent.com/tjt263/macports-installer/master/macports-installer.sh)"
  

• Install Nmap

  $ sudo port install nmap
  

• Optional

  $ sudo port search nmap
  $ sudo port info nmap
  

The package manager for MacOS

A package manager that people often use with MacOS, is Homebrew,

To install nmap, using Homebrew-

http://brewformulas.org/Nmap

brew install nmap

Additional notes
Your question is largely answered at this unix.stackexchange link. https://unix.stackexchange.com/questions/80711/how-to-install-apt-get-or-yum-on-mac-os-x So, apt-get is not really recommended as a package manager for MacOS. Homebrew is one.. and another one called macports. ..Apparently you can get apt-get on macOS but getting it to work is, they say here, a bit advanced.

I suggest you learn your package manager, in the case of MacOS, macports or homebrew, learn how to get a list of packages, or search for a package e.g. search for nmap, see the command to search or list packages and to install a package. that's if google fails to bring up the homebrew command to install nmap. Though google threw up for me http://brewformulas.org/Nmap brew install nmap

As of May 20, 2020, the homebrew installer fails to install something called nmap-scripts. This means nmap will work for some scans, but as you start to go deeper, you may see error messages like this:

nmap -p 1-65535 -T4 -A -v example.com
Starting Nmap 7.70 ( https://nmap.org ) at 2020-05-20 13:25 JST
Unable to find nmap-services!  Resorting to /etc/services
NSE: failed to initialize the script engine:
could not locate nse_main.lua
stack traceback:
    [C]: in ?

QUITTING!

This Link explains what is missing. Unfortunately that package is not available through homebrew at the moment.

The most foolproof way at the moment is to either use a different package manager (both fink and macports are endorsed by nmap.org), build it from source, or download the installer from nmap.org. All methods are explained here.