HTML DOM and JavaScript

HTML DOM and JavaScript Interaction

• The HTML DOM enables JavaScript to interact with and manipulate web page structure and content.
• The DOM represents an HTML document as a tree-like structure.
• In the DOM, elements are considered nodes.
• JavaScript can modify all HTML elements on a page.
• JavaScript's capabilities include adding new HTML elements.
• JavaScript cannot remove existing HTML elements.
• Elements can be selected by their ID using document.getElementById('id').
• The syntax element.style.property = value is used to manipulate elements.
• New elements are added dynamically with document.createElement().
• appendChild() does not remove elements.
• Events facilitate responses to user interactions.
• addEventListener() doesn't overwrite existing event handlers.
• Multiple event handlers of the same type can be added to an element.
• The third parameter of addEventListener() is not mandatory.
• HTML events are actions or occurrences that happen to HTML elements.
• JavaScript can react to HTML events.

Selecting HTML Elements

• The correct method to select an HTML element by its ID is document.getElementById('id').
• DOM stands for Document Object Model.
• Compiling JavaScript code is not a valid JavaScript DOM operation.
• document.getElementsByClassName('class') is used to select elements by their class name.
• The addEventListener() method attaches an event handler to a specified element.
• Any number of event handlers can be added to one element.
• The first parameter of addEventListener() specifies the event type,
• The second parameter of the addEventListener() method specifies the function to be called when an event occurs.
• The return type of document.getElementById() is a single element object.
• The 'click' event executes when the user clicks on an element.
• The onmouseover event occurs when the user moves the mouse over an HTML element.

JSON (JavaScript Object Notation)

• A JSON file stores simple data structures and objects in JavaScript Object Notation format.
• JSON is primarily for transmitting data between client and server.
• JSON files are not heavy and hard to read.
• JSON cannot natively represent seven types of data.
• JSON objects are not created by square brackets.
• JSON doesn't allow trailing commas after the last entry in an object or array.
• Most programming languages have built-in JSON support.
• In JavaScript, JSON.stringify() is not used to decode JSON strings.
• JSON data cannot include comments.
• JSON does not let you define a schema.
• The Fetch API is a modern JavaScript interface for making network requests.
• The Fetch API is not based on callbacks.
• The fetch() function returns a Promise.
• Fetch rejects the promise for HTTP errors such as 404 or 500.
• Multiple JSON files can be fetched using multiple fetch() calls and coordinating with Promises.
• The file extension .json is used when saving a JSON file.
• Function is not a JSON data type.
• Curly braces {} are used to create JSON objects.
• JSON.stringify() is used to convert a JavaScript object to a JSON string.
• JSON.parse() is used to convert a JSON string to a JavaScript object.
• A limitation of JSON is its lack of data types.
• The Fetch API primarily enables making network requests.
• The fetch() function returns a Promise.
• response.json() is used to parse the response body as JSON.
• When Fetch encounters an HTTP error like 404, the promise is resolved.

PHP (Hypertext Preprocessor)

• PHP stands for PHP: Hypertext Preprocessor.
• PHP scripts aren't executed on the client-side.
• PHP files cannot only contain PHP code.
• PHP can create, open, read, write, delete, and close files on the server.
• PHP is not only compatible with Windows servers.
• PHP code is enclosed within <?php and ?> tags.
• PHP keywords are not case-sensitive.
• PHP variable names are case-sensitive.
• The PHP echo statement does not have a return value.
• PHP automatically assigns a data type to a variable.
• PHP supports more than just string and integer data types.
• Constants in PHP cannot be changed during script execution.
• Constants are automatically global across the entire script.
• PHP superglobals are not only accessible within functions.
• $_POST variable isn't used to collect values from HTML forms using the GET method.
• The if-else statement allows code execution based on a condition.
• A for loop continues until a condition is met.
• A do-while loop executes the code block at least once.
• Foreach loop is used to iterate over arrays.
• PHP functions are declared using the 'function' keyword.
• PHP arrays can store values other than strings.
• Associative arrays do not use integer indices.
• The array_push function does not remove the last element of an array.
• array_merge function merges two arrays into one.
• The round() function can round a number down to the nearest integer.
• The empty() function checks if a variable is set.
• PHP filters are used for validating and sanitizing data.
• password_hash() function uses a one-way hashing algorithm.
• Object is not a valid PHP data type.
• The file extension for PHP files is .php.
• The $ symbol is used to declare a variable in PHP.
• echo() function is used to output data to the screen in PHP.
• echo is faster than print.
• define() function is used to create a constant in PHP.
• $_POST superglobal variable collects data from HTML forms using the POST method.
• The do-while loop in PHP executes a block of code at least once.
• The sort() function sorts an array in ascending order.
• The array_push() function adds an element to the end of an array.
• max() is used to find the function to find the highest value among arguments
• The ceil() function rounds a number up to the nearest integer.
• isset() function checks if a variable is set and not NULL.
• PHP filters' purpose is to validate and sanitize data.
• password_hash() function is used to create a password hash.