slevithan / regex-utilities

Tiny helpers for processing regex syntax

regex-utilities

Tiny utilities that the regex library makes available for reuse in its plugins. Useful for parsing and processing regular expression syntax in a lightweight way, when you don't need a full regex AST.

Constants

Context

Frozen object with the following properties for tracking regex syntax context:

• DEFAULT - Base context.
• CHAR_CLASS - Character class context.

Functions

For all of the following functions, argument expression is the target string, and needle is the regex pattern to search for.

• Argument expression (the string being searched through) is assumed to be a flag-v-mode regex pattern string. In other words, nested character classes within it are supported when determining the context for a match.
• Argument needle (the regex pattern being searched for) is provided as a string, and is applied with flags su.
• If argument context is not provided, matches are allowed in all contexts. In other words, inside and outside of character classes.

execUnescaped

Arguments: expression, needle, [pos = 0], [context]

Returns a match object for the first unescaped instance of a regex pattern in the given context, or null.

hasUnescaped

Arguments: expression, needle, [context]

Checks whether an unescaped instance of a regex pattern appears in the given context.

forEachUnescaped

Arguments: expression, needle, callback, [context]

Runs a callback for each unescaped instance of a regex pattern in the given context.

replaceUnescaped

Arguments: expression, needle, replacement, [context]

Replaces all unescaped instances of a regex pattern in the given context, using a replacement string or callback.

Examples

const str = '.\\.\\\\.[[\\.].].';
replaceUnescaped(str, '\\.', '@');
// → '@\\.\\\\@[[\\.]@]@'
replaceUnescaped(str, '\\.', '@', Context.DEFAULT);
// → '@\\.\\\\@[[\\.].]@'
replaceUnescaped(str, '\\.', '@', Context.CHAR_CLASS);
// → '.\\.\\\\.[[\\.]@].'

getGroupContents

Arguments: expression, contentsStartPos

Extracts the full contents of a group (subpattern) from the given expression, accounting for escaped characters, nested groups, and character classes. The group is identified by the position where its contents start (the string index just after the group's opening delimiter). Returns the rest of the string if the group is unclosed.