index.js

'use strict';
var fs = require('fs');
var path = require('path');

var commentRx = /^[ \t]*(?:\/\/|\/\*)[@#][ \t]+sourceMappingURL=data:(?:application|text)\/json;base64,(.+)(?:\*\/)?/mg;
var mapFileCommentRx =
  // //# sourceMappingURL=foo.js.map                       /*# sourceMappingURL=foo.js.map */
  /(?:^[ \t]*\/\/[@|#][ \t]+sourceMappingURL=(.+?)[ \t]*$)|(?:^[ \t]*\/\*[@#][ \t]+sourceMappingURL=(.+?)[ \t]*\*\/[ \t]*$)/mg

function decodeBase64(base64) {
  return new Buffer(base64, 'base64').toString();
}

function stripComment(sm) {
  return sm.split(',').pop();
}

function readFromFileMap(sm, dir) {
  // NOTE: this will only work on the server since it attempts to read the map file

  var r = mapFileCommentRx.exec(sm);
  mapFileCommentRx.lastIndex = 0;
  
  // for some odd reason //# .. captures in 1 and /* .. */ in 2
  var filename = r[1] || r[2];
  var filepath = path.join(dir, filename);

  try {
    return fs.readFileSync(filepath, 'utf8');
  } catch (e) {
    throw new Error('An error occurred while trying to read the map file at ' + filepath + '\n' + e);
  }
}

function Converter (sm, opts) {
  opts = opts || {};
  try {
    if (opts.isFileComment) sm = readFromFileMap(sm, opts.commentFileDir);
    if (opts.hasComment) sm = stripComment(sm);
    if (opts.isEncoded) sm = decodeBase64(sm);
    if (opts.isJSON || opts.isEncoded) sm = JSON.parse(sm);

    this.sourcemap = sm;
  } catch(e) {
    console.error(e);
    return null;
  }
}

Converter.prototype.toJSON = function (space) {
  return JSON.stringify(this.sourcemap, null, space);
};

Converter.prototype.toBase64 = function () {
  var json = this.toJSON();
  return new Buffer(json).toString('base64');
};

Converter.prototype.toComment = function () {
  var base64 = this.toBase64();
  return '//# sourceMappingURL=data:application/json;base64,' + base64;
};

// returns copy instead of original
Converter.prototype.toObject = function () {
  return JSON.parse(this.toJSON());
};

Converter.prototype.addProperty = function (key, value) {
  if (this.sourcemap.hasOwnProperty(key)) throw new Error('property %s already exists on the sourcemap, use set property instead');
  return this.setProperty(key, value);
};

Converter.prototype.setProperty = function (key, value) {
  this.sourcemap[key] = value;
  return this;
};

Converter.prototype.getProperty = function (key) {
  return this.sourcemap[key];
};

exports.fromObject = function (obj) {
  return new Converter(obj);
};

exports.fromJSON = function (json) {
  return new Converter(json, { isJSON: true });
};

exports.fromBase64 = function (base64) {
  return new Converter(base64, { isEncoded: true });
};

exports.fromComment = function (comment) {
  comment = comment
    .replace(/^\/\*/g, '//')
    .replace(/\*\/$/g, '');

  return new Converter(comment, { isEncoded: true, hasComment: true });
};

exports.fromMapFileComment = function (comment, dir) {
  return new Converter(comment, { commentFileDir: dir, isFileComment: true, isJSON: true });
};

// Finds last sourcemap comment in file or returns null if none was found
exports.fromSource = function (content) {
  var m = content.match(commentRx);
  commentRx.lastIndex = 0;
  return m ? exports.fromComment(m.pop()) : null;
};

// Finds last sourcemap comment in file or returns null if none was found
exports.fromMapFileSource = function (content, dir) {
  var m = content.match(mapFileCommentRx);
  mapFileCommentRx.lastIndex = 0;
  return m ? exports.fromMapFileComment(m.pop(), dir) : null;
};

exports.removeComments = function (src) {
  commentRx.lastIndex = 0;
  return src.replace(commentRx, '');
};

exports.removeMapFileComments = function (src) {
  mapFileCommentRx.lastIndex = 0;
  return src.replace(mapFileCommentRx, '');
};

exports.__defineGetter__('commentRegex', function () {
  commentRx.lastIndex = 0;
  return commentRx; 
});

exports.__defineGetter__('mapFileCommentRegex', function () {
  mapFileCommentRx.lastIndex = 0;
  return mapFileCommentRx; 
});