核心代码：

function co(generator) {

  return function(fn) {

  var gen = generator();

  function next(err, result) {

    if(err){

      return fn(err);

    }

    var step = gen.next(result);

    if (!step.done) {

      step.value(next);

    } else {

      fn(null, step.value);

    }

  }

  next();

   }

}

用法：

var co = require('./co');

// wrap the function to thunk

function readFile(filename) {

    return function(callback) {

      require('fs').readFile(filename, 'utf8', callback);

    };

}

co(function * () {

    var file1 = yield readFile('./file/a.txt');

    var file2 = yield readFile('./file/b.txt');

    console.log(file1);

    console.log(file2);

    return 'done';

})(function(err, result) {

    console.log(result)

});

会打印出：

content in a.txt

content in b.txt

done

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generator_co:  http://liuxinxiu.com/generator_co/