Calling a function of a Node.js module from a module

Question

I am trying to write a node module to clear my code and split it into different files.

Consider the code below:

module.exports = { Hello : function(request, reply) { return reply("Hello " + World()); }, World : function() { return "World"; } } 

If I import the above module and use the Hello function as a handler for a specific route, I get an internal HTTP 500 server error.

I narrowed down the problem to calling World () if I changed the Hello function to

 Hello : function(request, reply) { return reply("Hello World"); } 

Then it works fine, so it seems to work when another function is called from the export object

Does anyone know why this is happening and how to solve it?

Answer 1

You should call it like this:

 module.exports = { Hello: function(request, reply) { return reply("Hello " + module.exports.World()); }, World: function() { return "World"; } } 

If you are aiming for cleaner code, I suggest you change the code to this:

 function World() { return "World"; } function Hello(request, reply) { return reply("Hello " + World()); } module.exports = { Hello, } 

This will make your code more readable and you will only export what you really need. This question has other solutions to your problem.

Answer 2

Well demonstrate this

this does not determine the object this function is in. It determines which function is called. So for now;

 var obj = { Hello : function(request, reply) { return reply("Hello " + this.World()); }, World : function() { return "World"; } }; obj.Hello("test", console.log); 

will work fine; It will not be;

 var obj = { Hello : function(request, reply) { return reply("Hello " + this.World()); }, World : function() { return "World"; } }; setTimeout(obj.Hello,100,"test",console.log); 

This only happens because obj.Hello will be assigned an argument in the definition of the setTimeOut function, and this argument will be called as window , which is this for this function. So you should do like this:

 var obj = { Hello : function(request, reply) { return reply("Hello " + this.World()); }, World : function() { return "World"; } }; setTimeout(obj.Hello.bind(obj),100,"test",console.log); //or setTimeout(obj.Hello.bind(obj,"test",console.log),100); //or setTimeout((x,y) => obj.Hello(x,y),100,"test",console.log); 

Answer 3

You need to add this to your World() call -

 module.exports = { Hello : function(request, reply) { return reply("Hello " + this.World()); }, World : function() { return "World"; } } 

World is an attribute of an export object, not a variable in an accessible area - so you need to indicate that the function belongs to this .