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@ofjansen/pcre2-wasm
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PCRE2 (Perl Compatible Regular Expressions) compiled to WebAssembly for use in the browser.
npm install @ofjansen/pcre2-wasm
Internally this module uses the PCRE2 library, running in a WebAssembly instance. This has a side effect of requiring you do a few unusual things when using this module:
Before calling any constructors or methods, you must first asynchronously initialize the module by calling init
.
import libpcre2 from '@ofjansen/pcre2-wasm';
async function main () {
const lib = libpcre2();
lib.PCRE.init();
// make other PCRE calls...
}
main()
When you create a new PCRE
instance, you are allocating memory within the
WebAssembly instance. Currently, there are no hooks in JavaScript that
let us automatically free this memory when the PCRE
instance is garbage
collected by the JavaScript runtime. This means that in order to prevent
memory leaks, you must call .destroy()
on a PCRE
instance when it
is no longer needed.
import libpcre2 from '@ofjansen/pcre2-wasm';
const lib = libpcre2();
PCRE.init()
Initializes the module, returning a Promise that is resolved once
initialization is complete. You must call this at least once and await the
returned Promise before calling any other PCRE
methods or constructors.
PCRE.version()
Returns a string with the PCRE2 version information.
new PCRE(pattern, flags)
Creates a new PCRE instance, using pcre2_compile()
to compile pattern
,
using flags
as the compile options. You must call .destroy()
on the
returned instance when it is no longer needed to prevent memory leakage.
pattern
: A string containing a Perl compatible regular expression.
Tip: use String.raw
to avoid needing to escape backslashes.flags
: An optional string with each character representing an option.
Supported flags are i
, m
, s
, and x
. See
perlre for details.const pattern = String.raw`\b hello \s* world \b`
const re = new PCRE(pattern, 'ix')
// ...
re.destroy()
In the event of a compilation error in the pattern or an unsupported flag, an Error
will be thrown with an error message from PCRE2. Additionally, it will have an offset
property indicating the character offset in pattern
where the error was encountered.
let re
try {
re = new PCRE(String.raw`a)b`)
}
catch (err) {
console.error(`Compilation failed: ${err.message} at ${err.offset}.`)
// Prints: Compilation failed: unmatched closing parenthesis at 1.
}
re.destroy()
Releases the memory allocated in the WebAssembly instance. You must call this method manually once you no longer have a need for the instance, or else your program will leak memory.
re.match(subject, startOffset?)
Match the subject
against the regular expression, starting at startOffset
if specified (otherwise, start at position 0).
Returns an object that lists numbered and named captures, each with a start
, end
, and match
field.
For example, matching 000123
against /^(?<leading_zeros>0+).*$/
would result in the following object:
{
length: 1,
0: { start: 0, end: 6, match: "000123" },
1: { start: 0, end: 4, match: "000" },
leading_zeros: { start: 0, end: 4, match: "000" }
}
On no match, returns null
.
On an error, throw
s an Error
object whose string is a PCRE2 error name from PCRE2.h
.
re.matchAll(subject, startOffset?)
Returns an array of re.match()
results.
On no match, returns an empty array []
.
On an error, throw
s an Error
object whose string is a PCRE2 error name from PCRE2.h
.
re.substitute(subject, replacement, startOffset?)
Performs a single substitution on subject
against the regular expression, using replacement
, starting at startOffset
if specified (otherwise 0).
Returns a string.
On an error, throw
s an Error
object whose string is a PCRE2 error name from PCRE2.h
.
re.substituteAll(subject, replacement, startOffset?)
Performs all substitutions on subject
against the regular expression, using replacement
, starting at startOffset
if specified (otherwise 0).
Returns a string.
On an error, throw
s an Error
object whose string is a PCRE2 error name from PCRE2.h
.
re.exec(subject, global?)
If global
is specified and is truthy, will execute matchAll()
; otherwise executes match()
.
Prerequisites for development include Docker, make
, and curl
. All emscripten compiles (via emcc
) are done in docker containers to control the build environment.
This is a fork of stephen-riley/pcre2-wasm, with minor adjustments to make it work in a browser application I'm working on.
FAQs
PCRE2 (Perl Compatible Regular Expressions 2) compiled to WebAssembly for use in the browser
We found that @ofjansen/pcre2-wasm demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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