Mastering JavaScript Concepts

What are the different data types in JavaScript?

• undefined, null, boolean, number, string, symbol, object

• text, date, binary

• array, tuple, set

• integer, float, character

How do you declare a variable in JavaScript?

• You declare a variable using 'define'.

• You can only use 'let' to declare variables.

• You declare a variable in JavaScript using 'var', 'let', or 'const'.

• Variables are declared with 'declare'.

What is the difference between 'let', 'const', and 'var'?

• 'var' is function/global scoped, 'let' is block scoped and reassignable, 'const' is block scoped and not reassignable.

• 'const' is global scoped and reassignable

• 'var' is block scoped and not reassignable

• 'let' is function scoped and not reassignable

Explain the concept of scope in JavaScript.

• Scope in JavaScript is determined by the order of variable declarations.

• JavaScript has only one type of scope: global scope.

• Scope only applies to functions, not variables.

• Scope in JavaScript defines the visibility and lifetime of variables and functions, with global and local scopes being the primary types.

What is a function in JavaScript?

• A function is a type of object that cannot be reused.

• A function is a variable that holds a single value.

• A function in JavaScript is a reusable block of code that can take inputs, execute code, and return a value.

• A function is a method to store data in JavaScript.

How do you define a function in JavaScript?

• function:myFunction(param1, param2) => { // function body }

• function myFunction(param1, param2) { // function body } or const myFunction = (param1, param2) => { // function body }

• myFunction(param1, param2) { // function body }

• const myFunction = function(param1, param2) // function body

What is the purpose of the 'return' statement in a function?

• To define a function's parameters.

• To exit a function and return a value to the caller.

• To pause the function execution temporarily.

• To create a loop within the function.

How can you handle events in JavaScript?

• Use 'handleEvent' to respond to events in JavaScript.

• Use 'onclick' to handle events in JavaScript.

• Use 'addEventListener' to handle events in JavaScript.

• Use 'eventHandler' to manage events in JavaScript.

What is an event listener in JavaScript?

• An event listener is a type of loop that runs continuously.

• An event listener is a function that listens for and responds to events on a target element in JavaScript.

• An event listener is a variable that stores event data.

• An event listener is a method that only triggers on mouse clicks.

How do you prevent the default action of an event?

• Use event.cancelBubble = true;

• Use event.stopPropagation() in the event handler.

• Use event.preventDefault() in the event handler.

• Call event.returnValue = false;