NodeJS导出类与静态方法

Question

I'm trying to develop a class with static methods on a NodeJs application, as a Config module purpose.
I would like to access to it from different modules without instantiate every time a new object.

1) Is it correct to use an approach like below, avoiding the class prototype?

function Config(){

}

Config.svrPort=function(){
    return 8080;
}

Config.dbName=function(){
    return "myDbName";
}

module.exports = Config;

2) Are there any other solutions?

3) Is it also a valid approach to put different objects in the same module (eg config.js) like this?

exports.server=function(){
    return{
        port:8080
    };
};

exports.database=function(){
    return{
        name:"myDbName",
        user:"root",
        password:"myPassword",
        host:"localhost",
        port:3306
    };
};

and finally to use it as:

var config = require('./config');
config.server().port
config.database().name

Answer 1

That is the correct approach although in your example you could simply store the values as primitives: Config.SVR_PORT = 8080 , note I rewrote those as "constants", since I don't recommend changing statics.

When this is said, then please note: Do not put any sensitive data (passwords, etc) in your JavaScript files, but instead put these in a config file. This will separate config from code. And help you not to leak any potential critical information.

db-secrets.json

{
  "password": "...",
  ...
}

Then you can access the secrets by making a wrapper module:

// Wrapper module for db-secrets.json
var fs = require('fs');
exports = JSON.parse(fs.readFileSync('db-secrets.json'), 'utf8');

Or make a db connect module db-connect.js :

var fs = require('fs');
var db = require('db');
var db_secrets = JSON.parse(fs.readFileSync('db-secrets.json'), 'utf8');

export = function() {
  return db.connect(db_secrets.user, db_secrets.password, ...);
};

If you use git for source control you can easily add the following to your .gitignore which will make sure your sensitive file is not added to git:

.gitignore

db-secrets.json

Answer 2

There are no classes in the prototype languages (it's just a syntax sugar that mimics the classical OOP). Hence no static methods. My guess is that you want a singleton (which is the same as object literal ).

var Config = {
    get svrPort() {
        return 8080;
    },

    get dbName() {
        return "myDbName";
    },
};

// updated: https://nodejs.org/api/modules.html#modules_caching
// module.exports = Object.create(Config);
module.exports = Config;

Answer 3

JS supports object literals, not to mention that you can export a single object, or multiple export properties on the default exports object... When the require('./your-module'); happens the code in the module is not run again, it simply returns the original export, that has it's own original context.

---

Just export each of the functions/variables that you want as either an object literal, or attached to the exports.

//just declare any private context as it's own variables in your module, these are static
var someVal = "this isn't visible outside the module";

//export single object, with methods attached
//  NOTE: by default exports exists, and is already module.exports
//  exports === module.exports
exports = module.exports = { 
  getSomeVal: function getSomeVal(){
    return someVal;
  },
  getSrvPort: function getSrvPort(){
    return 8000;
  }
  ...
}

//alternatively, export each method as property
//    note, you should name your function assignments, 
//    this helps with debugging.
exports.getDbName = function getDbName(){
  return "mydb";
};

The code only actually runs once and all places using it will see the same option.

---

As an aside, if you're using Babel with ES6 modules, you can simply declare your export with each method...

export function getSrvPort() {
  return 8000;
}

export function dbName() {
  return "mydb";
}