JavaScript is a programming language that can be used to create interactive web pages. To understand how JavaScript works on the web, it's important to first understand how the web itself works.
Web pages are created using a combination of HTML, CSS, and JavaScript. HTML provides the structure of the page, CSS is used to style the page, and JavaScript adds interactivity and functionality to the page.
When you visit a website in your web browser, the browser sends a request to the server where the website is hosted. The server then sends back the files needed to display the website in your browser, including the HTML, CSS, and JavaScript files.
Once these files are downloaded by the browser, the HTML file is parsed and a Document Object Model (DOM) is created. The DOM is a tree-like structure that represents the elements on the web page. JavaScript can then be used to manipulate the DOM, adding or removing elements, changing styles, or responding to user interactions.
For example, let's say you have a button on your web page with an id of "myButton". You could use JavaScript to add a click event listener to the button, so that when someone clicks it, a message appears on the screen:
const myButton = document.getElementById("myButton");
myButton.addEventListener("click", function () {
alert("Hello, world!");
});In this example, we're using the getElementById method to get a reference to the button element on the page. We then use the addEventListener method to add a click event listener to the button. When the button is clicked, the anonymous function passed as the second argument to addEventListener is executed, which displays an alert message.
JavaScript can also be used to make requests to the server without reloading the entire page. This is called AJAX (Asynchronous JavaScript and XML). For example, you could use JavaScript to send a request to a server to get data and then update the page without refreshing it:
fetch("/api/data")
.then((response) => response.json())
.then((data) => {
// Do something with the data, like update the DOM
})
.catch((error) => {
console.error(error);
});In this example, we're using the fetch method to make a request to a server endpoint at /api/data. The then method is used to handle the response from the server. We convert the response to JSON format using the json method, and then use the data to update the DOM or do some other operation. If an error occurs, the catch method is used to handle it.
Overall, JavaScript is a powerful language for adding interactivity and functionality to web pages. By manipulating the DOM, making AJAX requests, and handling events, you can create dynamic and engaging web experiences for your users.
JavaScript में सर्वर एक कंप्यूटर होता है जो अन्य कंप्यूटर को डेटा और संसाधनों के लिए सेवा प्रदान करता है। सर्वर जीवन में बहुत महत्वपूर्ण होता है, जिसमें उपयोगकर्ता अन्य संसाधनों जैसे कि फ़ाइल, डेटाबेस और वेब पृष्ठों आदि तक पहुंच प्राप्त कर सकते हैं।
एक साधारण उदाहरण समझने के लिए, आप एक वेबसाइट खोलते वक्त सर्वर से संपर्क करते हो। जब आप वेबसाइट पते को अपने ब्राउज़र में भरते हो, तो आपका ब्राउज़र उस URL को सर्वर के पते तक भेजता है।
सर्वर, फिर उस URL के आधार पर डेटा और संसाधनों को ढूंढता है और अपने उपयोगकर्ताओं के लिए उन्हें भेजता है। उदाहरण के लिए, आप सर्वर से एक वेब पृष्ठ की जानकारी (HTML, CSS, फ़ोटो, वीडियो आदि) मांग सकते हैं।
इसके अलावा, सर्वर डेटाबेस से भी जुड़ा होता है जो उपयोगकर्ताओं के लिए डेटा को संग्रहित करता है। उदाहरण के लिए, एक ई-कॉमर्स वेबसाइट आपके खाते और खरीदों को एक डेटाबेस में संग्रहित करता है।
Client in JavaScript refers to the part of a web application that runs on the user's browser. When a user requests a webpage from the server, the server sends back HTML, CSS, and JavaScript files to the client's browser. The client then renders the webpage using these files.
JavaScript runs on the client-side, which means it is executed on the user's computer rather than on the server. This allows for dynamic and interactive features on a webpage, such as form validation, animations, and responsive design.
Let me explain this in Hinglish:
Client ka matlab hota hai wo hissa jise hum user ke browser mein use karte hain. Jab kabhi koi user server se webpage request karta hai toh server usko HTML, CSS aur JavaScript files bhejta hai. Fir client un files ko use karke webpage ko render karta hai.
JavaScript client-side pe chalta hai, matlab ye user ke computer pe execute hota hai aur server pe nahi. Isse webpage pe dynamic aur interactive features add kar sakte hai jaise form validation, animations aur responsive design.
For example, let's say you are visiting a website that has a form where you need to enter your name and email address. When you submit the form, JavaScript can validate whether you have entered a valid email address or not. It can also display an error message if any required fields are left blank.
Another example is when you visit a website that has a menu bar with dropdown options. JavaScript can be used to make the menu responsive, meaning it will adjust based on the size of the user's screen. Additionally, JavaScript can create animations when the user hovers over the menu options, making the website more engaging and interactive.
Request in JavaScript refers to the process of sending a network request to a server to retrieve or manipulate data. It can be used to fetch data from APIs, submit form data, or perform other types of HTTP requests.
For example, suppose you want to fetch data from an API using JavaScript. You can do so by creating a new instance of the XMLHttpRequest object, which allows you to send HTTP requests and receive responses.
Here's an example code snippet that demonstrates how to fetch data from an API using JavaScript:
var request = new XMLHttpRequest();
request.open('GET', 'https://api.example.com/data');
request.onload = function() {
if (request.status === 200) {
// Do something with the retrieved data
console.log(request.response);
} else {
// Handle errors
console.log('Error retrieving data');
}
};
request.send();
In this example, we create a new XMLHttpRequest object and specify the URL of the API we want to fetch data from. We then set up an event listener for the onload event, which is triggered when the response is received. If the response status is 200 (OK), we log the response to the console. Otherwise, we log an error message.
Overall, the XMLHttpRequest object allows us to send requests to a server and handle the responses in our JavaScript code.
Response ka matlab hai "javasript ke dwara prapt uttar", jo hum apne JavaScript code ko chalate samay aata hai. Jab hum kisi URL ki request bhejte hain, to server uske pehle uski authenticity aur security ko verify karke usi URL par corresponding data ka response bhejta hai. Is response mei hume us webpage ke HTML, CSS, aur JavaScript code ke sath-sath anya details jaise images ya database entries bhi mil sakte hain.
Jab tak hum JavaScript ke ajax API ka use nahi karte hain, tab tak hume browser ke dvara automatically ek page refresh hona padega. Lekin jab hum response ka use karte hain, tab hum server se data asynchrnously (bina page refresh ke) receive kar sakte hain aur use apne webpage par display kar sakte hain.
Example ke tor par, consider karein ki humare paas ek search box hai aur hum user ke dwara input kiye gaye keywords ke hisab se related results dikhana chahte hain. Jab user search button par click karte hain, tab hum JavaScript ka use karke unke dwara diye gaye keywords ko server ke paas bhej sakte hain aur server uska response ek JSON object ke roop mei bhej sakta hai. Us JSON object ko hum phir apne webpage par parse karke dikhane ke liye use kar sakte hain.