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What is the best way to expose methods from Node.js?

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[前端(javascript) 所属分类 前端(javascript) | 发布者 店小二05 | 时间 2018 | 作者 红领巾 ] 0人收藏点击收藏

Consider I want to expose a method called Print

Binding method as prototype :

File Saved as Printer.js

var printerObj = function(isPrinted) { this.printed = isPrinted; } printerObj.prototype.printNow = function(printData) { console.log('= Print Started ='); }; module.exports = printerObj;

Then access printNow() by putting code require('Printer.js').printNow() in any external .js node program file.

Export method itself using module.exports :

File Saved as Printer2.js

var printed = false; function printNow() { console.log('= Print Started ='); } module.exports.printNow = printNow;

Then access printNow() by putting code require('Printer2.js').printNow() in any external .js node program file.

Can anyone tell what is the difference and best way of doing it with respect to Node.js ?

Problem courtesy of: Amol M Kulkarni

Solution

Definitely the first way. It is called the substack pattern and you can read about it on Twitter and on Mikeal Rogers' blog . Some code examples can be found at the jade github repo in the parser:

var Parser = exports = module.exports = function Parser(str, filename, options){ this.input = str; this.lexer = new Lexer(str, options); ... }; Parser.prototype = { context: function(parser){ if (parser) { this.contexts.push(parser); } else { return this.contexts.pop(); } }, advance: function(){ return this.lexer.advance(); } };

Solution courtesy of: zemirco

Discussion

In the first example you are creating a class, ideally you should use it with "new" in your caller program:

var PrinterObj = require('Printer.js').PrinterObj; var printer = new PrinterObj(); printer.PrintNow();

This is a good read on the subject: http://www.2ality.com/2012/01/js-inheritance-by-example.html

In the second example you are returning a function.

The difference is that you can have multiple instances of the first example (provided you use new as indicated) but only one instance of the second approach.

Discussion courtesy of: Hector Correa

This recipe can be found in it's original form on Stack Over Flow .

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