how to ignore a file for git in by creating .gitignore file? code example

Example 1: how to create gitignore

# Don't track content of these folders
node_modules/
someOtherfoler/


# Compiled source #
###################
*.com
*.class
*.dll
*.exe
*.o
*.so

*.so

# Packages #
############
# it's better to unpack these files and commit the raw source
# git has its own built in compression methods
*.7z
*.dmg
*.gz
*.iso
*.jar
*.rar
*.tar
*.zip

Example 2: what to add to gitignore

Look at this awesome site!
https://www.toptal.com/developers/gitignore
Generates a gitignore for you, based on the technologies you're using