depending/index.js

Find out which modules depend on a given module

var slice = Array.prototype.slice;
var fs = require('fs');
var path = require('path');

exports.scan =
function scan(dirs) {
  var d = depending;

  if (! arguments.length) throw new Error('Nothing to scan');
  dirs = slice.call(arguments);
  dirs = reduce(dirs, []);
  d.dirs = dirs;
  d.packages = [];

  var dependings = {}; // reverse dependence  tree

  scan(dirs);


  function depending(package) {
    return dependings[package] || [];
  }

  function addDependency(from, to) {
    if (! dependings[to]) dependings[to] = [];
    dependings[to].push(from);
  }

  function scanPackage(packagePath) {
    var package = require(packagePath);
    d.packages.push(package);
    var name = package.name
    if (name && package.dependencies) {
      Object.keys(package.dependencies).forEach(function(dep) {
        addDependency(name, dep);
      });
    }
  }

  function scanDir(dir) {
    var packagePath = path.join(dir, 'package.json');
    if (fs.existsSync(packagePath)) {
      scanPackage(packagePath);
    } else {
      if (fs.statSync(dir).isDirectory()) {
        var files = fs.readdirSync(dir);
        files.forEach(function(f) {
          scanDir(path.join(dir, f));
        });
      }
    }
  }

  function scan(dirs) {
    dirs.forEach(scanDir);
  }

  return d;

}


function reduce(dirs, previous) {
  return dirs.reduce(function(previous, dir) {
    if (Array.isArray(dir)) previous = reduce(dir, previous);
    else previous.push(dir);
    return previous;
  }, []);
}