同步捕获
异步捕获
异常抛出

代码：https://github.com/fengchunjian/nodejs_examples/tree/master/routerv6

//models/Exception.js
module.exports = {
    expfun : function(flag) {
        if (flag == 0) {
            throw "我是例外";
        }
        return "success";
    }
}

//models/optfile.js
var fs = require('fs')
module.exports = {
    readImg : function(path, res) {
        fs.readFile(path, "binary", function(err, file) {
            if (err) {
                console.log(err);
                return;
            } else {
                console.log("异步读取图片完成");
                res.write(file, "binary");
                res.end();
            }
        });
    },
    writefile : function(path, data, recall) {
        fs.writeFile(path, data, function(err) {
            if (err) {
                throw err;
            }
            console.log("异步写文件完成");
            recall("异步写文件完成");
        });
    },
    readfile : function(path, recall) {
        fs.readFile(path, function(err, data) {
            if (err) {
                console.log("异步捕获异常:"+err);
                recall("异步捕获异常:"+err.toString());
            } else {
                recall(data);
            }
        });
        console.log("异步读文件完成");
    },
}

//models/router.js
var optfile = require("./optfile");
var exception = require("./Exception");
function getRecall(req, res) {
    res.writeHead(200, {'Content-Type':'text/html;charset=utf-8'});
    function recall(data) {
        res.write(data);
        res.end();
    }
    return recall;
}
module.exports = {
    testexp : function(req, res) {
        recall = getRecall(req, res);
        try {
            data = exception.expfun(0);
            recall(data);
        } catch(err) {
            console.log("捕获自定义异常:"+err);
            recall("捕获自定义异常:" + err.toString());
        }
    },
    readImg : function(req, res) {
        res.writeHead(200, {'Content-Type':'image/jpeg'});
        optfile.readImg("./imgs/nodejs.jpg", res);
    },
    writefile : function(req, res) {
        recall = getRecall(req, res);
        optfile.writefile("./file.txt", "异步文件写入", recall);
    },
    login : function(req, res) {
        recall = getRecall(req, res);
        optfile.readfile("./views/loginx.html", recall);
    },
    zhuce : function(req, res) {
        recall = getRecall(req, res);
        optfile.readfile("./views/zhuce.html", recall);
    }
}

//routercall.js
var http = require('http');
var url = require('url');
var router = require('./models/router');
http.createServer(function (request, response) {
    if(request.url!=="/favicon.ico") {
        var pathname = url.parse(request.url).pathname;
        pathname = pathname.replace(/\//, '');
        try {
            router[pathname](request, response);
        } catch(err) {
            console.log("同步捕获异常:"+err);
            response.writeHead(200,{'Content-Type':'text/html;charset=utf-8'});
            response.write("同步捕获异常:"+err.toString());
            response.end();
        }
        console.log("主程序执行完毕");
    }
}).listen(8000);
console.log('Server running at http://127.0.0.1:8000/');

node routercall.js
Server running at http://127.0.0.1:8000/
异步读文件完成
主程序执行完毕
异步捕获异常:Error: ENOENT: no such file or directory, open './views/loginx.html'
异步读文件完成
主程序执行完毕
同步捕获异常:TypeError: router[pathname] is not a function
主程序执行完毕
捕获自定义异常:我是例外
主程序执行完毕

curl http://localhost:8000/login
异步捕获异常:Error: ENOENT: no such file or directory, open './views/loginx.html'
curl http://localhost:8000/zhuce
注册界面
curl http://localhost:8000/xxx
同步捕获异常:TypeError: router[pathname] is not a function
curl http://localhost:8000/testexp
捕获自定义异常:我是例外

参考文档

nodejs9_异常处理(n9_exception)
http://www.yuankuwang.com/web/index.php?r=respool/resview&rpid=42
node.js教程9_异常处理
http://edu.51cto.com/center/course/lesson/index?id=124533