JavaScript Interview Questions for Freshers

JavaScript Interview Questions for Freshers

Source:- JavaScript Developer Interview Questions for Freshers

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1. What are the data types in JavaScript ?

In JavaScript, data types can be categorized into two main groups: primitive and non-primitive (also known as reference types) data types. Here’s an explanation of each:

1. Primitive Data Types:

These are immutable data types that store a single value.

a. Boolean: Represents a logical value, either true or false. It is commonly used for conditions and branching in JavaScript.

let isTrue = true;
let a=5;
let isFalse = false;
console.log(isTrue);   // Output: true
console.log(isFalse);  // Output: false

b. Number: Represents numeric values, including integers and floating-point numbers.

let count = 10;
let price = 4.99;
console.log(count);  // Output: 10
console.log(price);  // Output: 4.99
undefined

c. String: Represents a sequence of characters enclosed in single or double quotes. Strings are used to represent textual data.

let message = "Hello, world!";
console.log(message);  // Output: Hello, world!
undefined

d. Null: Represents the intentional absence of any object value. It is often assigned to a variable to indicate that it has no value or that the value is unknown.

let value = null;
console.log(value);  // Output: null
undefined

e. Undefined: Represents an uninitialized or undeclared variable. If a variable is declared but not assigned a value, it will have the value of undefined.

let variable;
console.log(variable);  // Output: undefined
undefined

f. Symbol: Represents a unique identifier. Symbols are typically used as keys in objects to avoid naming conflicts.

let id = Symbol("unique");
console.log(id);  // Output: Symbol(unique)
undefined

2. Non-Primitive (Reference) Data Types:

These are mutable data types that store references to memory locations rather than the actual values.