Global objects in Node.pdf

Global objects in Node.pdf

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  Global objects inNode.js One of the key features of Node.js is the availability of global objects. These objects are accessible throughout your application without requiring explicit declaration, making them convenient for various tasks. We will explore some of the essential global objects in Node.js and demonstrate their usage with code examples. __filename: In Node.js, the ‘__filename’ global object provides the absolute path of the current module file. It represents the filename of the script that is currently being executed. In this section, we will explore the usage of the ‘__filename’ global object with a code example. console.log(__filename); When you execute the above code in a Node.js application, it will print the absolute path of the current module file, including the filename. For example: /home/user/project/app.js The ‘__filename’ global object is particularly useful when you want to access the file path or extract information about the current module being executed. It allows you to dynamically reference the current file within your code.
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  Here’s a practicalexample that demonstrates the usage of ‘__filename’: const path = require('path'); console.log(`The current script is located at: ${__filename}`); const directory = path.dirname(__filename); console.log(`The current script is in the directory: ${directory}`); __dirname: In Node.js, the ‘__dirname’ global object represents the directory name of the current module file. It provides the absolute path of the directory containing the currently executing script. In this section, we will explore the usage of the ’ __dirname’ global object with a code example. console.log(__dirname); When you execute the above code in a Node.js application, it will print the absolute path of the directory containing the current module file. For example: /home/user/project/ The ‘__dirname’ global object is useful when you want to access the directory path or resolve file paths relative to the current module. Here’s a practical example that demonstrates the usage of ‘__dirname’: const path = require('path');
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  console.log(`The current scriptis located in the directory: ${__dirname}`); const filePath = path.join(__dirname, 'data', 'file.txt'); console.log(`The absolute path to file.txt is: ${filePath}`); Global Objects: The ‘global’ object is the root object of the Node.js runtime environment. It provides properties and methods that are available globally in your application. While using global objects is generally discouraged due to potential naming conflicts, understanding their capabilities is crucial. Here’s an example: // Accessing global object properties console.log(global.process); // Access the 'process' object // Modifying global object properties global.myVariable = 'Hello, Global!'; console.log(myVariable); // Hello, Global! Console Objects: The ‘console’ object provides methods for writing output to the console, which is useful for debugging and logging messages. Here’s an example of how to use it: // Logging messages to the console
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  console.log('This is alog message'); console.error('This is an error message'); console.warn('This is a warning message'); Process Objects: The ‘process’ object provides information and controls over the current Node.js process. It contains properties and methods that allow you to interact with the environment, access command-line arguments, and more. Here’s an example: // Accessing process-related information console.log(process.pid); // Process ID console.log(process.cwd()); // Current working directory console.log(process.argv); // Command-line arguments Module Objects: The ‘module’ object represents the current module in Node.js. It contains information about the current module, such as its filename, exports, and more. Let’s see an example: // Accessing module-related information console.log(module.filename); // File name of the current module console.log(module.exports); // Exported objects and functions Require Function:
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  Although not aglobal object itself, the ‘require’ function is a fundamental part of Node.js. It allows you to load external modules and their functionality into your application. Here’s a basic usage example: // Loading a module using 'require' const fs = require('fs'); // Load the 'fs' module for file system operations fs.readFile('example.txt', 'utf8', (err, data) => { if (err) throw err; console.log(data); }); It’s worth noting that the global objects mentioned above are just a subset of what Node.js offers. There are additional global objects and functions available that serve specific purposes, such as ‘setTimeout’, ‘setInterval’, ‘clearTimeout’, ‘clearInterval’, and more. 1. setTimeout FUNCTION: The ‘setTimeout()’ function allows you to execute a specified function after a specified delay in milliseconds. Here’s an example: // Call a function after a delay of 2 seconds setTimeout(() => { console.log('2 seconds have passed'); }, 2000); In the above example, the ‘setTimeout()’ function calls the provided function after a delay of 2 seconds.
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  2. setInterval FUNCTION: The’setInterval()’function enables you to periodically call a certain function after a given milliseconds-long delay. Here’s an example: // Call a function repeatedly after a delay of 1 second const intervalId = setInterval(() => { console.log('1 second has passed'); }, 1000); 3. clearTimeout FUNCTION: The ‘clearTimeout()’ function is used to stop the execution of a function that was scheduled to run after a specified delay using ‘setTimeout()’. Here’s an example: // Call a function after a delay of 2 seconds and then stop it using clearTimeout() const timeoutId = setTimeout(() => { console.log('2 seconds have passed'); }, 2000); clearTimeout(timeoutId); // Stop the execution of the above function In the above example, the ‘setTimeout()’ function calls the provided function after a delay of 2 seconds. The ‘clearTimeout()’ function is then used to stop the execution of the function.
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  4. clearInterval FUNCTION: The‘clearInterval()’ function is used to stop the execution of a function that was scheduled to run repeatedly using ‘setInterval()’. Here’s an example: // Call a function repeatedly after a delay of 1 second and then stop it using clearInterval() const intervalId = setInterval(() => { console.log('1 second has passed'); }, 1000); clearInterval(intervalId); // Stop the execution of the above function In the above example, the ‘setInterval()’ function calls the provided function repeatedly after a delay of 1 second. The ‘clearInterval()’ function is then used to stop the execution of the function. While global objects provide convenience, it’s generally recommended to limit their usage and opt for modular code. Excessive reliance on global objects can lead to potential conflicts and make your code harder to maintain and test. function printHello() { console.log( "Hello, World!"); } // Now call above function after 2 seconds var timeoutObj = setTimeout(printHello, 2000); 5. TextEncoder:
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  The TextEncoder classis used to encode JavaScript strings into a specified character encoding. It provides the encode() method to convert a string into an encoded Uint8Array 6. TextDecoder: The TextDecoder class is used to decode binary data, such as Uint8Array, into JavaScript strings using a specified character encoding. It provides the decode() method to convert the encoded data into a string. By using ‘TextEncoder’ and ‘TextDecoder’, you can handle text encoding and decoding in different character encodings, allowing you to work with data in various formats. These classes are particularly useful when dealing with network communication, file I/O, or any scenario where you need to convert text between different encodings. 7. URLSearchParams: The URLSearchParams is a built-in JavaScript class that provides utility methods for working with the query parameters of a URL. It allows you to parse, manipulate, and serialize query strings in a convenient manner. The URLSearchParams class is particularly useful when dealing with URLs and handling query parameters dynamically. const paramsString = 'name=John&age=25&city=New York'; const searchParams = new URLSearchParams(paramsString); console.log(searchParams.get('name')); // John console.log(searchParams.get('age')); // 25
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  console.log(searchParams.get('city')); // NewYork searchParams.append('country', 'USA'); searchParams.set('age', '30'); console.log(searchParams.toString()); // name=John&age=30&city=New+York&country=USA Conclusion: Understanding the global objects in Node.js is crucial for building robust server-side applications. By leveraging the capabilities of these global objects, you can streamline your development process and enhance the functionality of your Node.js applications.