learnyounode Lesson 5

课程目标：

Create a program that prints a list of files in a given directory,
  filtered by the extension of the files. You will be provided a
  directory name as the first argument to your program (e.g.
  '/path/to/dir/') and a file extension to filter by as the second
  argument.

课程思路：

• 使用fs.readdir()异步读取文件夹数据
• 在readdir()的回调函数中处理文件列表
• 使用path.extname()方法获取文件后缀

My Solution:

var fs = require("fs");
var path = require("path");

var folder = process.argv[2];
var ext = "." + process.argv[3];

fs.readdir(folder, function(err, files) {
  if (err) return console.error(err);
  files.forEach(function(file) {
    if (path.extname(file) === ext) {
      console.log(file);
    }
  });
});

课程总结

1. node异步函数采用回调函数的方法处理数据
2. path.extname()返回的后缀名带有.