JavaScript, as a dynamically-typed language, provides two distinct primitive values to represent the absence of a meaningful value: undefined and null. Although they might seem similar at first glance, they have different meanings and behaviors. Understanding the difference between undefined and null is crucial for writing clean and bug-free JavaScript
Ruby, a dynamic, object-oriented programming language, offers several methods for outputting information to the console. Among the commonly used ones are puts, print, and p. While they might seem similar at first glance, each serves a distinct purpose in Ruby programming. Let’s delve into each of these methods to understand
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NodeJS is a popular back-end JavaScript runtime that is used for building server-side applications. In this section, we will cover the NodeJS programming fundamentals and provide some code samples to demonstrate these concepts.
To set up a NodeJS project, we first need to install NodeJS on our local machine. Once installed, we can create a new NodeJS project using the following steps:
1. Create a new directory for the project.
2. Open the command prompt and navigate to the project directory.
3. Run npm init command to initialize the project and create a package.json file. This
file contains metadata about the project, including the dependencies required for the project.
NodeJS uses the concept of event-driven programming to handle requests and responses. When a request is made, NodeJS creates an event, and a callback function is executed when the event is triggered. Here is a simple example of how to handle requests and responses using NodeJS:
const http = require('http');
const server = http.createServer((req, res) => {
res.write('Hello World!');
res.end();
});
server.listen(8080, () => {
console.log('Server started on port 8080');
});
In this example, we use the http module to create a new HTTP server. The createServer() method takes a callback function that is executed whenever a new request is made to the server. We write the response using the res.write() method and end the response using the res.end() method.
NodeJS is designed to handle asynchronous programming using callbacks, promises, and async/await. Here is an example of how to use callbacks in NodeJS:
function fetchData(callback) {
setTimeout(() => {
callback('Data fetched successfully');
}, 2000);
}
fetchData((data) => {
console.log(data);
});
In this example, we create a function called fetchData that takes a callback function as a parameter. The fetchData function simulates fetching data by using the setTimeout() function to delay the execution of the callback for 2 seconds. When the callback function is executed, we pass in the data that was fetched as a parameter.
NodeJS allows us to organize our code into modules that can be reused across different parts of our application. Here is an example of how to create a simple module in NodeJS:
// greet.jsfunction greet(name) {
console.log(`Hello ${name}!`);
}
module.exports = greet;
In this example, we create a module called greet that exports a function that takes a name parameter and logs a greeting to the console. The module.exports object is used to export the greet function so that it can be used in other parts of our application.
We can then use the greet module in our main application file as follows:
const greet = require('./greet');
greet('John');
In this example, we use the require() function to import the greet module into our main application file. We can then use the greet function to log a greeting to the console.
These are just a few of the many fundamental concepts of NodeJS programming. Understanding these concepts will help you build robust, scalable, and efficient NodeJS applications.
1. Set up the project by creating a new directory for the project and running npm init to create a package.json file
2. Install the necessary dependencies, including express and axios, by running the command npm install express axios.
3. Create a new file called index.js and import the required modules:
const express = require('express');
const axios = require('axios');
const app = express();
const port = 3000;
4. Define the routes to interact with the external API. For example, to retrieve all articles, we can create a GET request handler:
app.get('/articles', async (req, res) => {
try {
const response = await axios.get('https://external-api.com/articles');
res.send(response.data);
} catch (error) {
res.status(500).send(error);
}
});
axios module to make a GET request to the external API and retrieve all articles. We then send the data back to the client using the res.send() method. If an error occurs, we send a 500 status code and the error message using the res.status() and res.send() methods.5. Set up the project by creating a new directory for the project and running npm init to create a package.json file
app.post('/articles', async (req, res) => {
try {
const response = await axios.post('https://external-api.com/articles', req.body);
res.send(response.data);
} catch (error) {
res.status(500).send(error);
}
});
app.put('/articles/:id', async (req, res) => {
try {
const response = await axios.put(`https://external-api.com/articles/${req.params.id}`, req.body);
res.send(response.data);
} catch (error) {
res.status(500).send(error);
}
});
app.delete('/articles/:id', async (req, res) => {
try {
const response = await axios.delete(`https://external-api.com/articles/${req.params.id}`);
res.send(response.data);
} catch (error) {
res.status(500).send(error);
}
});
axios module to make POST, PUT, and DELETE requests to the external API to create, update, and delete articles. We pass in the article data as the request body and the article ID as a URL parameter. We then send the response data back to the client using the res.send() method. If an error occurs, we send a 500 status code and the error message using the res.status() and res.send() methods.6. Finally, we start the server by listening on the specified port:
app.listen(port, () => {
console.log(`Server listening at http://localhost:${port}`);
});
