M4 NPM | npm.io

m4

Work in progress!

m4 is a pure Javascript implementation of an m4 macro language processor. You can use it with Node.js or in the browser, via browserify. It is exposed as a transformation Stream. As such, you can easily pipe from any input and to any output.

A command-line version is also provided, usable as a drop-in replacement for a native version (such as GNU M4).

Installation

npm install m4

If installed locally, the binary is available as node_module/.bin/m4. You can directly refer to m4 in npm-scripts.

Example usage

From a shell

echo "define(\`beep', \`boop')dnl\nbeep\n" | m4
#=>  boop

From JavaScript

// example.js
'use strict';

var M4 = require('m4');

var input = new M4();
input.pipe(M4()).pipe(process.stdout);

input.write("define(`beep', `boop')dnl\nbeep\n");
input.end();

Then, in a shell:

node example.js
#=>  boop

API

Class: M4

Inherit stream.Transform. As such this is a duplex stream you can pipe, write and read.

new M4(opts)

opts Object Options:
- nestingLimit Number Maximum nested macro calls. Beware, this does not prevent endless rescanning loops.

Event: 'error'

Signal a non-recuperable error. The stream will not produce further output in the case of an error.

Event: 'warning'

Signal a warning. The steam continues to produce output normally, but there may be some unwanted behavior.

m4.define(name, {fn|str})

name String Identifier.
fn Fonction Called with (name, [arg1, arg2 ... ]), must return the macro expansion result as a string. name is the macro defined name itself.
str String Macro content, just like you were defining the macro in M4.

Define a M4 macro as a Javascript function.

m4.divert(index=0)

index Number Diversion index.

Change how the output is processed. If the index is zero, output is directly emitted by the stream. If the index is a positive integer, the output is stored in an internal buffer — a "diversion" — instead.