JavaScript Variables & Hoisting Quiz

Explain the difference between var, let, and const in terms of scope.

• let is function-scoped, var and const are block-scoped.

• const is function-scoped, var and let are block-scoped.

• var is block-scoped, let and const are function-scoped.

• var is function-scoped, let and const are block-scoped. const variables cannot be reassigned.

Consider this code snippet:

console.log(a); // What will be the output?

var a = 10; console.log(a); // What will be the output?

• The first output will be 'undefined' and the second output will be '10'.
• The first output will be 'null' and the second output will be '10'.
• The first output will be '0' and the second output will be '10'.
• The first output will be '10' and the second output will be 'undefined'.

What is hoisting in JavaScript?

• Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope before code execution.

• Hoisting is a JavaScript concept that refers to the process of optimizing code execution for faster performance.

• Hoisting is a JavaScript feature that allows variables to be declared without using the 'var' keyword.

• Hoisting is a JavaScript mechanism where variables and function declarations are moved to the bottom of their scope before code execution.

Consider this code snippet:

{

let d = 25;

}

console.log(d); // What will be the output?

• 25
• undefined
• ReferenceError

• true

When should you use const over let in JavaScript?

• When the variable is declared inside a function

• When the variable will be reassigned multiple times

• When the variable is used in a loop

• When the variable will not be reassigned

What is the difference between global and local scope in JavaScript?

• Global scope variables are only accessible within the function they are declared in.

• Global scope variables are accessible from anywhere in the code, while local scope variables are only accessible within the function they are declared in.

• Local scope variables are accessible from anywhere in the code.

• Global scope variables are limited to a specific block of code.

What type of error happens if you try to access a variable before it is declared in JavaScript?

• SyntaxError

• TypeError

• RuntimeError

• ReferenceError

Consider this code snippet:

console.log(b); // What will be the output?

let b = 15;

console.log(b); // What will be the output?

• The output will be: 15, 0
• The output will be: 15, undefined
• The output will be: ReferenceError, 15

• The output will be: 0, 15

Consider this code snippet:

{

var c = 20;

}

console.log(c); // What will be the output?

• ReferenceError

• 10
• 20
• undefined

How does the use of var, let, and const impact memory management in JavaScript?

• Var, let, and const in JavaScript determine the order of execution of variables in memory.

• The use of var, let, and const impacts memory management in JavaScript by defining the color of variables in memory.

• The use of var, let, and const impacts memory management in JavaScript by defining how variables are stored in memory. 'var' variables are function-scoped and can be redeclared and updated, potentially leading to memory leaks. 'let' variables are block-scoped and can be updated but not redeclared, providing better memory management. 'const' variables are also block-scoped but cannot be reassigned, ensuring memory integrity.

• Using var, let, and const in JavaScript has no impact on memory management.