JavaScript Fundamentals Quiz

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Questions and Answers

What is the purpose of the 'this' keyword in JavaScript?

To refer to the previous object
To refer to the global object
To refer to the current object (correct)
To refer to the parent object

What is the difference between 'var' and 'let' keywords in JavaScript?

Var is used for function scope and let is used for block scope (correct)
Var is used for global variables and let is used for local variables
Var is used for local variables and let is used for global variables
Var is used for block scope and let is used for function scope

What is the purpose of the 'prototype' property in JavaScript?

To inherit properties from another object (correct)
To delete a property from an object
To create a new object
To add a new property to an object

What is the difference between 'null' and 'undefined' in JavaScript?

Null is used to represent an empty value and undefined is used to represent an uninitialized variable (C) Signup and view all the answers

What is the purpose of the 'bind' method in JavaScript?

To call a function with a specific context (A) Signup and view all the answers

In JavaScript, what happens when you use the 'delete' operator on a property?

It removes the property from the object (C) Signup and view all the answers

What is the purpose of the 'call' method in JavaScript?

To call a function with a different 'this' context (D) Signup and view all the answers

What happens when you try to access a non-existent property in JavaScript?

It returns undefined (C) Signup and view all the answers

What is the purpose of the 'apply' method in JavaScript?

To call a function with an array of arguments (B) Signup and view all the answers

What is the purpose of the 'arguments' object in JavaScript?

To access the parameters of a function (D) Signup and view all the answers

Study Notes

JavaScript Key Concepts

The this keyword in JavaScript refers to the current execution context of the function, allowing it to dynamically change its value based on how the function is called.

Variable Declarations

var keyword declares a variable that is scoped to the nearest function block, allowing it to be re-declared and updated within its scope, whereas let keyword declares a variable that is block-scoped, meaning it cannot be re-declared within its scope.

Object-Oriented Programming

The prototype property in JavaScript is used to create a new object that inherits properties and behavior from an existing object, allowing for inheritance and polymorphism.

Data Types

null represents the intentional absence of any object value, whereas undefined represents an uninitialized or non-existent variable or property.

Function Binding

The bind method in JavaScript creates a new function that has the same function body as the original function, but with a bound this context, allowing it to be called with a specific context.

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Description

Test your knowledge of basic JavaScript concepts, including 'this', 'var', 'let', 'prototype', 'null', 'undefined', and 'bind'. Prepare for your JavaScript interview!