dst.js

class User {
}
class Something {
}
User.defineRelationship('Something', { to: 'one' });

dumper.js

var esprima = require('esprima');
var fs = require('fs');

var srcDir = './samples/js/';
var dstDir = './samples/ast/';

fs.readdir(srcDir, function(err, files){
  if (err) throw err;
  files.forEach(function(fileName) {
    fs.readFile(srcDir + fileName, function(err, code) {
      if(err) throw err;
      var ast = esprima.parse(code);
      var outPath = (dstDir + fileName).replace(/.js/, '.ast.json');
      fs.writeFile(outPath, JSON.stringify(ast, null, 2), function(err) {
        if(err) throw err;
        console.log(outPath);
      });
    });
  });
});

replace.js

'use strict';
var ast = require('./samples/ast/relation.ast.json');
var escodegen = require('escodegen');
var estraverse = require('estraverse');

ast = estraverse.replace(ast, {
  enter: function(node) {
    if (node.type === 'ExpressionStatement' && node.expression.type === 'Literal') {
      var m = node.expression.value.match(/(\w+)\s+has\s+(\w+)\s+(\w+)/);
      if (!m) this.skip();
      return {
        'type': 'ExpressionStatement',
        'expression': {
          'type': 'CallExpression',
          'callee': {
            'type': 'MemberExpression',
            'computed': false,
            'object': {
              'type': 'Identifier',
              'name': m[1]
            },
            'property': {
              'type': 'Identifier',
              'name': 'defineRelationship'
            }
          },
          'arguments': [{
            'type': 'Literal',
            'value': m[3],
            'raw': '\'' + m[3] + '\''
          }, {
            'type': 'ObjectExpression',
            'properties': [{
              'type': 'Property',
              'key': {
                'type': 'Identifier',
                'name': 'to'
              },
              'computed': false,
              'value': {
                'type': 'Literal',
                'value': m[2],
                'raw': '\'' + m[2] + '\''
              },
              'kind': 'init',
              'method': false,
              'shorthand': false
            }]
          }]
        }
      };
    }
  }
});

var code = escodegen.generate(ast);
console.log(code);

src.js

class User {
}

class Something {
}

"User has one Something";