JavaScript Functions and Events Mocktest

JavaScript functions are primarily used to create reusable code blocks. They encapsulate a set of statements to perform a specific task, which can be reused throughout the code. Functions enhance code organization, maintainability, and reusability.

The correct syntax for defining a JavaScript function is function functionName(parameters) { codeBlock }. Option A demonstrates this syntax with a function named addNumbers that takes num1 and num2 as parameters and returns their sum.

Parameters in a JavaScript function are used to accept inputs or values into the function. They act as placeholders that store the values passed to the function when it is called, allowing the function to work with dynamic data and perform operations based on the provided inputs.

An anonymous function in JavaScript is defined without a name. It can be assigned to a variable or passed as an argument to another function. Anonymous functions are often used as callbacks or for one-time use where a named function is not required or suitable.

In the given code, greet is an example of an anonymous function because it is assigned to a variable without a specific function name. Anonymous functions can be defined using the function keyword without a name and are commonly used for inline or one-time functions.

Events in JavaScript are used to handle user interactions and browser actions. They allow developers to respond to various actions performed by users, such as clicking buttons, submitting forms, hovering over elements, and more, making web pages interactive and dynamic.

The addEventListener() method is used to attach an event listener to an HTML element in JavaScript. It takes the event type (e.g., 'click', 'mouseover') and a callback function as parameters, allowing developers to define actions that occur when the specified event is triggered.

To prevent the default behavior of an event in JavaScript, you can use the event.preventDefault() method inside the event handler function. This method stops the browser from executing the default action associated with the event, such as submitting a form or following a link.

The onclick attribute in HTML elements is used to attach event listeners specifically for mouse clicks. When an element with the onclick attribute is clicked, the JavaScript code specified in the attribute is executed, allowing developers to define actions for mouse click events.

The onclick event is triggered when a user clicks on an HTML element. It is commonly used to handle click interactions, such as clicking buttons, links, or other clickable elements on a web page, and allows developers to define actions that occur when the element is clicked.