^

This matches the beginning of an input. If the multiline flag is set to true, it also matches immediately after the (\n) line break character.

/^ The/ matches "The" in "The stars", but not "In The stars".

$

This matches the end of an input. If the multiline flag is set to true, it also matches immediately before the (\n) line break character.

/and$/ matches "and" in "land", but not "and the bar".

\b

This matches any word boundary (test characters must exist at the beginning or at the end of a word within the string).

/va\b/ matches "va" in "this is a java script book", but not "this is a javascript book".

\B

This matches any non-word boundary.

/va\B/ matches "va" in "this is a JavaScript book", but not "this is a JavaScript book".