datacrow module already used by another module

#Datacrow module already used by another module code

The constructs - calculateArea and calculateCircumference, added to the module.exports, object are logged. The default value of module.exports object is exports is a key of the module object, the corresponding value of which is an object. The module parameter (rather a keyword in a module in Node) refers to the object representing the current module. Let’s discuss these two parameters in this article. So, the question that arises now is how do you specify something in a module that can be used by some other module? This is when the module & require parameters of the function wrapper are helpful. It means that you cannot use these constructs in any other module unless explicitly specified. An important point to keep in mind is that all these constructs are private to the circle module by default. There are three constructs defined in this module - a constant variable PI, a function named calculateArea and another function named calculateCircumference. Let’s revisit the circle module, which you looked at earlier. These parameters provide valuable information related to a module.

#Datacrow module already used by another module code

Though these parameters are global to the code within a module yet they are local to the module (because of the function wrapper as explained above). The five parameters - exports, require, module, _filename, _dirname are available inside each module in Node. (Remember each function in JavaScript has its own local scope?) This is the reason why module A cannot access the code written inside module B and vice-versa. Because the code pertaining to both the modules is enclosed within different functions, these functions will not be able to access the code of each other. Similar thing happens with the code written inside the module B. The code written inside the module A is enclosed within the function wrapper corresponding to the module A. Imagine that there are two modules - A and B. Code written inside a module is private to it! This happens because each module has a function wrapper of its own and the code written inside one function is local to that function and cannot be accessed outside this function. Even if you define a global variable in a module using var, let or const keywords, the variables are scoped locally to the module rather than being scoped globally. This is the most significant advantage of having modules in Node.js. The entire code written inside a module is private to the module, unless explicitly stated (exported) otherwise. You can see that there is a function wrapper at the root level encompassing all the code written inside the circle module.

The function wrapper for the circle module will look like the one given below: The syntax of this function wrapper is: All code you write in a module resides in the function wrapper! Too messy, right? How does the code written inside a module run?īefore executing the code written inside a module, Node takes the entire code and encloses it within a function wrapper. Imagine that there’s a large application and you have all your code written in just one place, just one file. By modular, I mean to say that your code should be independent and should be loosely coupled. Well, it is very important to write modular code. You might be wondering why is there a need to have multiple modules? You could have just written all the code in a single module. You can call circle.js file a module named circle. You have a file named circle.js which consists of the logic for calculating the area & the circumference of a circle of a given radius, as given below: Let’s take an example to understand this better. JavaScript file in Node.js corresponding to a ‘module’ By Srishti Gupta Everything you should know about ‘ module’ & ‘require’ in Node.js Modules Node.js treats each JavaScript file as a separate module.įor instance, if you have a file containing some code and this file is named xyz.js, then this file is treated as a module in Node, and you can say that you’ve created a module named xyz.