Node.js将命令行参数设置为常量

Question

I want to get an argv from my command line when I am going to start my server and then I want to set it as a constant for a module.

For example I want to define my log file path from commandline:

My starter.js looks like:

var optimist = require("optimist");
var server = require("./start_server");
var argv = optimist.describe('logpath', 'logptah for info').argv;
server.init({logpath:argv.logpath});

My start_server.js looks like:

    var restify = require('restify');
    var server = restify.createServer({
        name: 'dummy-project'
    });
    module.exports.logpath = null;
    function init(args){
        server.listen(1234, function() {
            console.log("inside logs");
            console.log(args.logpath);
            module.exports.logpath = args.logpath;
            console.log('%s listening at %s', server.name, server.url);
        });
    };
    module.exports.init = init;
    var fun = require('./common/loghandler');

My loghandler.js looks like:

var server = require('./../start_server');
console.log("inside log handler");
var LOGPATH = server.logpath;
console.log(LOGPATH);

When I am running node starter.js --logpath='../../custom/info.txt' I am not getting the logpath inside my loghandler.

Seems logpath handler is called before the server.listen.

The console output looks like:

node starter.js --logpath='../../custom/info.txt'
inside log handler
null
inside log handler 
../../custom/info.txt
dummy-project listening at http://0.0.0.0:1234

How I can overcome it and pass my log path as command line argument?

Thanks in advance.

Answer 1

Your init() function is executed after starter.js uses require('./start_server') . When you use require() , the file and all its dependencies are loaded. That means during this process, you also executed require('./common/loghandler') , which completes before server.init() is run in starter.js . Since server.logpath hasn't been set by this time, you get a null value.

Aside from that, module.exports is set at require time and changing the values later have no effect. To fix the problems you're having, you should avoid using functions before your application has fully loaded, and put return values in your modules.