newGulpFile = (filename, code) => {
    var src = require('stream').Readable({ objectMode: true })
    src._read = function () {
      this.push(new gutil.File({
        cwd: '',
        base: '',
        path: filename,
        contents: new Buffer(code)
      }))
      this.push(null)
    }
    return src
  }

newGulpFile(`a.js`, 'console.log("这里是要输出到文件的内容")').pipe(gulp.dest('/dist'))