Question

我正在进行学习练习。在此函数中，我按列表列出目录和过滤文件。据我了解，如果我提供一个无效的目录名，它应该进入if子句并退出。但相反，它转到if子句，然后抱怨else子句中的某些内容。

模块：

module.exports = function (path, ext, callb) {
    var fs = require('fs');
    var elems = [];
    var r = new RegExp("\\." + ext);
    fs.readdir(path, function (err, list) {
        console.log(err); // this runs, it's an object like { [Error: ENOENT, scandir '/Users/JohnnyLee/baobabf/
        console.log(list); // this also runs, it's undefined
        if (err) {
            console.log("ERR!!!"); // this ran!
            return callb(err);
        } else {
            console.log("NO ERRR!!!"); // this didn't run :/
            list.forEach(function (i) { // this crashes?
                if (i.match(r)) {
                    elems.push(i);
                }
            });
            return callb(err, elems);
        }
        console.log(list);
    });
};

可执行文件：

var mymod = require('./p06-1');
var filename = process.argv[2]
var extension = process.argv[3]

if (filename && extension) {
    mymod(filename, extension, function (err, list) {
        list.forEach(function (i) {
            console.log(i);
        });
    })
}

输出：

triton:learnnode JohnnyLee$ node p06-2.js doesntexist txt
{ [Error: ENOENT, scandir 'doesntexist'] errno: -2, code: 'ENOENT', path: 'doesntexist' }
undefined
ERR!!!
/Users/JohnnyLee/learnnode/p06-2.js:7
        list.forEach(function (i) {
            ^
TypeError: Cannot read property 'forEach' of undefined
    at /Users/JohnnyLee/learnnode/p06-2.js:7:13
    at /Users/JohnnyLee/learnnode/p06-1.js:11:20
    at FSReqWrap.oncomplete (fs.js:95:15)
triton:learnnode JohnnyLee$

我错过了什么：（？

Answer 1

你用：

来称呼它

mymod(filename, extension, function (err, list) {
    list.forEach(function (i) {
        console.log(i);
    });
})

那里的list.forEach错误。查看错误的文件名/行号。这是因为您在模块中致电callb(err)，但在假设list与class Comment(models.Model): article = models.ForeignKey(Article, null = True) comic = models.ForeignKey(Comic, null = True) assigned = models.BooleanField(initial=False)合作之前，您不会检查错误。

Answer 2

请正确检查错误堆栈，它响亮而清晰:)

关于你错过的问题，

添加错误检查语句以处理错误。修改mymod电话，如下所示，

if (filename && extension) {
    mymod(filename, extension, function (err, list) {
       if(err){
               //do something with error
          }else{
        list.forEach(function (i) {
            console.log(i);
                 }
        });
    })
}

为什么我的else语句在这段节点代码中运行？

2 个答案: