Ethan Hughes

Ethan Hughes


Truthy and Falsy: When All is Not Equal in JavaScript


Javascript is a programming language that does not strictly regulate the data type of variables (Weakly Typed Language). Therefore, depending on the case being used, the variable value in Javascript will be interpreted according to the appropriate data type.

For example:

var a = 1; // type int
var b = '2'; // type of string

console.log(a> b);
// result returned as `false`. Thus, the variable `b` is interpreted as type` int`

console.log(b + a);
// result will be "21". The variable `a` is interpreted with the type` string` ('2' + '1' = '21')

In another example, when the program wants the value of a variable to be returned as a type boolean, while that variable is defined with another type, the value of the variable will be interpreted in two truthy and falsy value groups .

var a = 1; // type int

console.log(a == false) // when comparing `a` (type` int`) to `false` (` `boolean`), the program wants a to be interpreted as` boolean`, then the value truthy or falsy of variables will be considered
// result returned as `false`. Why is it like that, I will explain below: D

So what is truthy and falsy value: -?


“Please tell us what is truthy and falsy value in Javascript?”

Perhaps this will be one of the most frequently asked questions in Javascipt interviews. And even myself and some of the others will be puzzled by this question because you don’t remember the exact values ​​or you don’t know it. So today I am determined to consolidate my knowledge and share with everyone about this issue, hoping to help you somewhat. (bow)

To put it simply … Truthy valueare values ​​in Javascript that when casted to Boolean will give the value is true. In contrast, Falsy valueare the values ​​that when cast to Boolean, the value is false.

In Javascript there are SIX values ​​considered falsy, all other values ​​which are not considered are considered truthy.

The way to remember data types is truthy and falsy value

  • The type Booleanhas a value trueand false, therefore, a false value is definitely a falsy value.
  • The type that Numbercontains all the numbers. But there are two special values: zero (0) and Not a Number (NaN), and it is both falsy value.
  • The string data type String, with empty strings (the string does not contain any characters) is the falsy value.
  • And there are 2 remaining values nulland undifinedfalsy value.

Bottom of the skirt is like this

DatatypesFalsy valueBooleanfalseNumber0 or NaNString’’ or ""nullnullundefinedundefined

Accomplished! I have listed it 6 falsy values, all the other values ​​are truthy.

For example some values ​​are truthy

  • “Any string” (any string including ‘0’, ‘false’)
  • [1, 2] (any array including empty array [])
  • {a: 1, b: 2} (any object including an empty object {})
  • function () {} (any function)

Looking at these examples, you can explain the examples I wrote above

Compare with logical operators ==

When comparing truthy valueand falsy valueusing operators, ==unintended cases can occur.

Conventions that:

  • false0empty numbers and strings ''are equivalent.
  • nulland undefinedare equivalent but they are not equivalent to any other value.
  • NaNis not equivalent to any value - including principal NaN.
  • Infinityis truthy but when compared to truegood false, the result always returns false.
  • An empty array has a value of truthy but when compared to truewill result in false, compared with that falsereturns true.

For example:

// all true
false == 0;
0 == '';
null == undefined;
[] == false;
!![0] == true;

// all false
false == null;
NaN == NaN;
Infinity == true;
[] == true;
[0] == true;

Compare with logical operators ===

The only exception is NaNstill not equivalent to any value, including itself.

A few tips when using tips

Avoid direct comparison of values

When you need to compare a value with boolean, you rarely need to compare them directly with trueor falsejust consider the value as truthy or falsy .

// instead of
if (x == false) // ...
// runs if x is false, 0, '', or []

// use
if (!x) // ...
// runs if x is false, 0, '', NaN, null or undefined

Use ===instead of==

When you need to compare two values ​​are the same or not, you should use the comparison operator ===(or !==) instead of ==(or !=) to avoid having problems of converting the value type.

// instead of
if (x == y) // ...
// runs if x and y are both truthy or both falsy
// e.g. x = null and y = undefined

// use
if (x === y) // ...
// runs if x and y are identical...
// except when both are NaN

Convert to value booleanas needed

Any value can be converted to value booleanusing the operator !! (Double Bangs). Use this operator for falsy valuefalse0'' or ""nullundefinedNaN) will receive the value of false, and are used when you want to check the value 2 is truthyor falsyor not?

// instead of
if (x === y) // ...
// runs if x and y are identical...
// except when both are NaN

// use
if (!!x === !!y) // ...
// runs if x and y are identical...
// including when either or both are NaN

#javascript #programming

What is GEEK

Buddha Community

Truthy and Falsy: When All is Not Equal in JavaScript

Rahul Jangid


What is JavaScript - Stackfindover - Blog

Who invented JavaScript, how it works, as we have given information about Programming language in our previous article ( What is PHP ), but today we will talk about what is JavaScript, why JavaScript is used The Answers to all such questions and much other information about JavaScript, you are going to get here today. Hope this information will work for you.

Who invented JavaScript?

JavaScript language was invented by Brendan Eich in 1995. JavaScript is inspired by Java Programming Language. The first name of JavaScript was Mocha which was named by Marc Andreessen, Marc Andreessen is the founder of Netscape and in the same year Mocha was renamed LiveScript, and later in December 1995, it was renamed JavaScript which is still in trend.

What is JavaScript?

JavaScript is a client-side scripting language used with HTML (Hypertext Markup Language). JavaScript is an Interpreted / Oriented language called JS in programming language JavaScript code can be run on any normal web browser. To run the code of JavaScript, we have to enable JavaScript of Web Browser. But some web browsers already have JavaScript enabled.

Today almost all websites are using it as web technology, mind is that there is maximum scope in JavaScript in the coming time, so if you want to become a programmer, then you can be very beneficial to learn JavaScript.

JavaScript Hello World Program

In JavaScript, ‘document.write‘ is used to represent a string on a browser.

<script type="text/javascript">
	document.write("Hello World!");

How to comment JavaScript code?

  • For single line comment in JavaScript we have to use // (double slashes)
  • For multiple line comments we have to use / * – – * /
<script type="text/javascript">

//single line comment

/* document.write("Hello"); */


Advantages and Disadvantages of JavaScript

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Hire Dedicated JavaScript Developers -Hire JavaScript Developers

It is said that a digital resource a business has must be interactive in nature, so the website or the business app should be interactive. How do you make the app interactive? With the use of JavaScript.

Does your business need an interactive website or app?

Hire Dedicated JavaScript Developer from WebClues Infotech as the developer we offer is highly skilled and expert in what they do. Our developers are collaborative in nature and work with complete transparency with the customers.

The technology used to develop the overall app by the developers from WebClues Infotech is at par with the latest available technology.

Get your business app with JavaScript

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Book Free Interview:

#hire dedicated javascript developers #hire javascript developers #top javascript developers for hire #hire javascript developer #hire a freelancer for javascript developer #hire the best javascript developers

Niraj Kafle


The essential JavaScript concepts that you should understand

As a JavaScript developer of any level, you need to understand its foundational concepts and some of the new ideas that help us developing code. In this article, we are going to review 16 basic concepts. So without further ado, let’s get to it.

#javascript-interview #javascript-development #javascript-fundamental #javascript #javascript-tips

Ajay Kapoor


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Santosh J


JavaScript compound assignment operators

JavaScript is unarguablly one of the most common things you’ll learn when you start programming for the web. Here’s a small post on JavaScript compound assignment operators and how we use them.

The compound assignment operators consist of a binary operator and the simple assignment operator.

The binary operators, work with two operands. For example a+b where + is the operator and the a, b are operands. Simple assignment operator is used to assign values to a variable(s).

It’s quite common to modify values stored in variables. To make this process a little quicker, we use compound assignment operators.

They are:

  • +=
  • -+
  • *=
  • /=

You can also check my video tutorial compound assignment operators.

Let’s consider an example. Suppose price = 5 and we want to add ten more to it.

var price = 5;
price = price + 10;

We added ten to price. Look at the repetitive price variable. We could easily use a compound += to reduce this. We do this instead.

price += 5;

Awesome. Isn’t it? What’s the value of price now? Practice and comment below. If you don’t know how to practice check these lessons.

Lets bring down the price by 5 again and display it.
We use console.log command to display what is stored in the variable. It is very help for debugging.
Debugging let’s you find errors or bugs in your code. More on this later.

price -= 5;

Lets multiply price and show it.

price *=5;

and finally we will divide it.

price /=5;

If you have any doubts, comment below.

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