Nodejs module without parameters - node.js

Question

I am developing a Nodejs module, which is a function and returns an object with a function in a property. If I call the module without any parameter returns error (Test is not a constructor). If I call the module passing a parameter, even if it is empty, it works properly.
Example #1
(App)
//var test = require('./index.js')().Test; // Works properly
var test = require('./index.js').Test;
var sample = new test('text', function(newText) {
console.log(newText);
});
(Module)
module.exports = function(options) {
var bold = 0;
var anotheModule = new anotherModule(options); //If the parameters are not defined, take the default.
console.log('Check 1');
return {
Test: Test
}
function Test(text) {
.....
}
}
Example #2
(Module)
module.exports = function textChange(options) {
var bold = 0;
var anotheModule = new anotherModule(options); //If the parameters are not defined, take the default.
console.log('Check 1');
}
textChange.prototype.Test = function(text) {
.....
}
Example #3
(Module)
function textChange(options) {
var bold = 0;
var anotheModule = new anotherModule(options); //If the parameters are not defined, take the default.
console.log('Check 1');
}
textChange.prototype.Test = function(text) {
.....
}
module.exports = textChange;
Example #4
(Module)
function textChange(options) {
var bold = 0;
var anotheModule = new anotherModule(options); //If the parameters are not defined, take the default.
console.log('Check 1');
}
Test = function(text) {
.....
}
module.exports = textChange;
export.Test = Test;
I can't get the solution to work without passing parameters. I can't get the solution to work without passing parameters. If the application calls the module with parameters, it works correctly.

Answer 1

The error Test is not a constructor that you're getting it is because you're using the new keyword on undefined. Since Test is undefined.
const test = undefined;
try {
new test();
} catch(e) {
console.log(e.message);
}
In your example #1 you're exporting a function that when executed returns an object containing Test, that's why you need to use () on the exported module.
In your example #2 & #3, you're exporting a function (constructor), so it is the instance of textChange which has the Test method:
const textChange = require('./index.js');
new textChange().Test();
Note: Your example #2 will throw a ReferenceError, textChange is not defined since you're assigning it directly to module.exports, so it should be:
module.exports = function textChange(options) {
var bold = 0;
console.log('Check 1');
}
module.exports.prototype.Test = function(text) {
/* ... */
}
In your last example, the last line: export should be exports but it won't do what you're expecting.
What's being exported it's module.exports, which is a function, textChange to be precise, so Test will never be available outside of that module.
var test = require('./module.js');
console.log(test.Test); // undefined
Check this question: module.exports vs exports in Node.js
I don't know exactly what you're trying to achieve, but if you want
var test = require('./index.js').Test;
You should export an object containing Test property.
Module
module.exports = {
Test(text) {
/* ... */
}
}
or
function Test(text) {
console.log('Text: ', text);
}
module.exports.Test = Test;