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Some tricky JavaScript questions you should know

Shahriar Saleh Fahim
Front-End Developer | Competitive Gamer 🎮
・2 min read

Hello, all!!! Hope you guys are safe. Today I'll talk about some tricky parts of JavaScript which you should definitely know to increase your knowledge in JS.

Truthy & Falsy Values

Let's start with the easy one. Sometimes you may write conditions where you would need to define if a variable is true theb it might do something and if it is false it might do something else. Here's an example

const age=4
if(age>0){
console.log('True')
}
else{
console.log('False')
}
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Here you declared a variable called age and gave a condition that if age>0 then it will print True otherwise it will print False. Pretty straight right? Even if you don't write age instead of age>0 it will still print True(Try yourself in a IDE). It's happening because as variable age has a value other than 0 ,assigned to it it will always return True . So 0 here is called a Falsy value in JS.

So can you guess what should happen if I create a variable named nameand assign empty string to it . What will be answer?

const name=''
if(name){
console.log('True')
}
else{
console.log('False')
}
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If you ran the code you know the result. The answer is False.So, you may already have a guess that JS basically treats any empty or null value as Falsy values. So you might be asking what about empty arrays and objects? Both of them are Truthy values because when you initiate an array or object without a property you are still creating a object. Objects are considered True in JS. Array is also a type of Object.

Below here is a list of Truthy and Falsy values in JS. Please also check them by yourselves in your IDE.

Falsy Values

number = 0
string = "" (no white space)
undefined
null
NaN
False

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Truthy Values

'0'
string = " " ( white space)
[] (empty array)
{} (empty object)
true
'false' (It's a string)
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