1. What is JavaScript?
JavaScript is a high-level, interpreted programming language primarily used for creating interactive web pages.
2. What are the different data types in JavaScript?
JavaScript supports various data types including strings, numbers, booleans, null, undefined, objects, and symbols (added in ES6).
3. How do you declare variables in JavaScript?
Variables in JavaScript can be declared using the var, let, or cons keywords.
4. What is the difference between let, const, and var?
var has function scope, let has block scope, and const is used to declare constants whose value cannot be reassigned.
5. What is the use of == and === operators in JavaScript?
== is used for loose equality comparison, whereas === is used for strict equality comparison, which checks both value and type.
6. How do you comment in JavaScript?
Single-line comments are denoted by //, and multi-line comments are enclosed between /* and */.
7. What are JavaScript primitive data types?
Primitive data types in JavaScript include strings, numbers, booleans, null, undefined, and symbols.
8. What is the typeof operator used for?
The typeof operator is used to determine the type of a variable or an expression.
9. Explain hoisting in JavaScript.
Hoisting is JavaScript's default behavior of moving variable and function declarations to the top of their containing scope during compilation.
10. What is NaN in JavaScript?
NaN stands for "Not-a-Number" and is a value returned when a mathematical operation cannot produce a meaningful result.