json header to yaml header

json-to-yaml.js

var fs = require('fs');
var YAML = require('json2yaml');

var layout = process.env.JEKYLL_POST_LAYOUT || "post";

process.stdin.on('data', function(d) {
  var files = d.toString().split('\n').filter(function(e){ return e !== ''; });
  files.map(function(fn) {
    var contents = fs.readFileSync(fn).toString();
    contents.replace(/({.*title.*})/m, function(match, p1, s) {
      var blob = JSON.parse(p1);
      blob.layout = layout;
      var yamlblob =  YAML.stringify(blob) + '---\n';
      fs.writeFileSync(fn, contents.replace(p1, yamlblob));
    });
  });
});