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Map()
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A JavaScript object that stores key-value pairs, where keys can be any type of data, and values can be any data type.
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set(key, value)
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Adds a new key-value pair to the Map. If the key already exists, it updates the value.
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get(key)
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Retrieves the value associated with the key from the Map. If the key doesn’t exist, returns undefined.
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has(key)
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Checks if a key exists in the Map. Returns true or false.
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delete(key)
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Removes a key-value pair from the Map.
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clear()
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Removes all key-value pairs from the Map.
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forEach(callback)
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Iterates over each key-value pair in the Map and executes a provided function.
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console.log()
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Outputs a message to the console, commonly used for debugging.
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let, const, var
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Variable declaration keywords: let (block-scoped), const (block-scoped and immutable), var (function-scoped).
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Promises
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Represents a value that may be available in the future. It is used for handling asynchronous operations.
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async/await
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Used to simplify asynchronous code. await waits for a promise to resolve, and async makes a function asynchronous.
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DOM (Document Object Model)
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The structure that represents the HTML document as a tree of nodes, allowing dynamic manipulation.
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AJAX (Asynchronous JavaScript and XML)
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Technique for making asynchronous HTTP requests to fetch data without refreshing the page.
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JSON (JavaScript Object Notation)
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Lightweight data-interchange format that’s easy for humans to read and write, and for machines to parse and generate.
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RESTful APIs
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Design principles for building web services that are stateless and use HTTP methods for CRUD operations (GET, POST, PUT, DELETE).
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CSS Flexbox
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Layout model that allows for responsive and flexible design, aligning elements in rows or columns.
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CSS Grid
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2D layout system for creating grid-based layouts with rows and columns.
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CORS (Cross-Origin Resource Sharing)
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A mechanism that allows restricted resources on a web page to be requested from another domain.
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express()
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The function used to create an instance of an Express application.
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app.listen(port)
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Starts the Express server and listens on a specified port. For example: app.listen(3000) to listen on port 3000.
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app.get(route, callback)
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Defines a route handler for GET requests. For example: app.get('/', (req, res) => res.send('Hello World'))
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app.post(route, callback)
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Defines a route handler for POST requests. For example: app.post('/submit', (req, res) => res.send('Data received'))
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app.put(route, callback)
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Defines a route handler for PUT requests. Typically used for updating data.
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app.delete(route, callback)
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Defines a route handler for DELETE requests. Usually used to remove resources.
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app.use(middleware)
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Adds middleware to the Express app. Middleware functions execute during the lifecycle of a request. For example: app.use(express.json()) to parse JSON in request bodies.
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res.send()
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Sends a response to the client. Can send various types of data such as strings, objects, or arrays.
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res.json()
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Sends a JSON response. Converts an object or array to JSON format.
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require()
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Imports modules, JSON, or local files into your Node.js application.
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fs module
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Provides an API for interacting with the file system, allowing you to read, write, and modify files.
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module.exports
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Defines what a module exports so that other files can use it.
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fs.readFile(path, encoding, callback)
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Asynchronously reads the contents of a file. The callback receives two arguments: an error (if any) and the data.
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fs.writeFile(path, data, encoding, callback)
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Asynchronously writes data to a file, replacing the file if it already exists. The callback handles error (if any).
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fs.appendFile(path, data, encoding, callback)
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Asynchronously appends data to a file. If the file does not exist, it is created. The callback handles error (if any).
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fs.copyFile(src, dest, callback)
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Asynchronously copies a file from src to dest. The callback handles error (if any).
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addEventListener()
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Attaches an event handler to an element for a specific event.
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removeEventListener()
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Removes an event handler from an element.
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event.target
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Returns the element that triggered the event.
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event.preventDefault()
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Cancels the default behavior of an event (e.g., prevents form submission).
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event.stopPropagation()
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Stops the event from propagating up or down the DOM tree.
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DOMContentLoaded
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Fires when the HTML has been completely loaded, but before stylesheets, images, and subframes finish loading.
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
