Logical Operators in JavaScript

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2 years ago

Logical Operators in JavaScript

In this post, we will give you information about Logical Operators in JavaScript. Here we will give you detail about Logical Operators in JavaScript And how to use it also give you a demo for it if it is necessary.

JavaScript has 3 logical operators:

!: Logical NOT
&&: Logical AND
||: Logical OR

Logical NOT

The logical not operator ! checks whether a value is truthy or falsy. In other words, !v === falseunlessv is one
of the below 7 values:

false
0n: 0 as a BigInt
'': Empty string
null
undefined
NaN

// Falsy values means '!v === true'
!false; // true
!0; // true
!''; // true
!undefined; // true
!null; // true
!Number('abc'); // true

// All other values are "truthy", meaning '!v === false'
!1; // false
!({}); // false
!({ valueOf: () => 0 }); // false
!' '; // false

The not operator always returns a boolean, unlike || and &&. A common
way to convert a value v to a boolean is to use the logical not operator twice:

// Convert 'v' to a boolean
!!v;

Logical OR

The logical or operator || operates on 2 values, and returns a truthy
value if at least one of the values is truthy.

// True if 'a' or 'b' is truthy. Will only be 'false' if
// both 'a' and 'b' are falsy.
!!(a || b);

The logical or operator is most often used in if statements to execute
the if block if one of multiple conditions is true. But, the logical
or operator does not necessarily return a boolean:

If a is truthy, (a || b) === a
If a is falsy, (a || b) === b

This works neatly with multiple or operators: a || b || c || d returns
the leftmost value that is truthy. Because of this, logical or is often
used for default values:

const defaultNumReps = 2;

function repeat(str, numReps) {
  // If 'numReps' is null, undefined, or 0, this sets
  // 'numReps' to the default value '2'
  numReps = numReps || defaultNumReps;

  let ret = '';
  for (let i = 0; i < numReps; ++i) {
    ret += str;
  }
  return ret;
}

Logical AND

The logical and operator && operates on 2 values, and returns falsy
if at least one of the values is falsy:

// Only true if both 'a' and 'b' are truthy.
!!(a && b);

The logical and operator is most often used in if statements to execute
the if block if multiple conditions are all true. But, like the logical
or operator, the logical and operator doesn’t necessarily return a boolean:

If a is falsy, (a && b) === a
If a is truthy, (a && b) === b

Given a chain of multiple logical and operators a && b && c && d, JavaScript
returns the left-most falsy value.

JavaScript Fundamentals for Logical Operators in JavaScript

JavaScript is a programming language that is used to create interactive web pages. It is a client-side scripting language, which means that it runs on the user’s browser. JavaScript can be used to add animation, interactivity, and functionality to web pages.

Here are some of the fundamentals of JavaScript:

Variables: Variables are used to store data. They are declared using the var keyword.
Data types: JavaScript has a variety of data types, including strings, numbers, booleans, objects, and arrays.
Operators: Operators are used to perform operations on data.
Control flow statements: Control flow statements allow you to control the order in which your code is executed.
Functions: Functions are blocks of code that can be reused.
Objects: Objects are used to store data in key-value pairs.
Arrays: Arrays are used to store data in a sequential order.
Events and event handlers: Events are notifications that are sent by the browser when something happens, such as when the user clicks on an element or moves the mouse over an element. Event handlers are functions that are called in response to an event.
DOM manipulation: The Document Object Model (DOM) is a tree-like structure that represents the elements of a web page. JavaScript can be used to manipulate the DOM to change the appearance or behavior of a web page.

These are just some of the fundamentals of JavaScript. There are many other concepts that you can learn as you continue to develop your skills.

Here are some resources that you can use to learn more about JavaScript:

Mozilla Developer Network (MDN): The MDN is a great resource for learning about JavaScript. It has a comprehensive reference guide, tutorials, and articles on a wide range of topics.
W3Schools: W3Schools is another great resource for learning about JavaScript. It has interactive tutorials and quizzes that can help you learn the basics of the language.
JavaScript.info: JavaScript.info is a website that provides in-depth tutorials on JavaScript. It also has a forum where you can ask questions and get help from other JavaScript developers.

I hope this helps!

Here are some additional tips for learning JavaScript:

Start with the basics: Before you start trying to build complex applications, it’s important to learn the basics of JavaScript. This includes things like variables, data types, operators, and control flow statements.
Practice regularly: The best way to learn JavaScript is to practice regularly. Try to find some time each day to work on JavaScript projects.
Get help from others: If you get stuck, don’t be afraid to ask for help from others. There are many online forums and communities where you can get help from other JavaScript developers.

With a little practice, you’ll be able to learn JavaScript and start building amazing web applications.

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