regexp-ranged-exec v0.1.1

RegExp Ranged Exec

Generate an enhanced exec function, with information about the range of text that the regex paid attention to.

This is useful for caching the result of a regex, or a series of regexes, when the portion of the input they looked at didn't change.

Details

• The calculated range is a conservative estimate and it's not precise for every regex.
• Regexes that capture everything, and have a single character class inside them, optionally followed by a quantifier, a character or a dot, produce the most precise ranges.
• Regexes that never match "\n" produce a range that is roughly the one containing the line that contains the index that the regex started matching from.
• All other regexes will give you a useless range, one enclosing the whole input.

Install

npm install --save regexp-ranged-exec

Usage

import getRangedExec from 'regexp-ranged-exec';

// You can create an enhanced "exec" function like this

const input = 'some aaa input';
const re = /([a]+)/;
const exec = getRangedExec ( re );
const execution = exec ( input );

// The execution object contains both whatever `RegExp.prototype.exec` would have given you, and the detected "range" for this match
// The range tells you how many characters to the left and right of the starting point the regex paid attention to
// If characters within that range don't change then it's guaranteed that the regex will return the same result
// The starting point of a regex is its "lastIndex" property, if the regex is either global or sticky, or 0 otherwise

const match = execution.result; // Whatever `RegExp.prototype.exec` returned
const range = execution.range; // [0, 9], the left and right offsets for this execution

License

MIT © Fabio Spampinato