Use [ x = y ] to compare values (or quote '==' if literal).

Problematic code:

if $var == value
then
  echo "Match"
fi

Correct code:

if [ "$var" = value ]
then
  echo "Match"
fi

Rationale:

ShellCheck found an unquoted == after a word.

This was most likely supposed to be a comparison, so use square brackets as in the correct code.

Exceptions:

If the == was supposed to be literal, you can quote it to make ShellCheck ignore it:

grep '===' file.js

Related resources:

• Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!