# Why do we use double in JavaScript?

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If you have ever noticed a double exclamation mark (!!) in someone’s JavaScript code you may be curious what it’s for and what it does. It’s really simple: it’s short way to cast a variable to be a boolean (true or false) value.

## What is the use of double in JavaScript?

The double-negation !! is not a distinct JavaScript operator nor a special syntax but rather just a sequence of two negations. It is used to convert the value of any type to its appropriate true or false Boolean value depending on whether it is truthy or falsy.

## What is the use of double not in JavaScript?

Double Negative (not) The single ! converts a value to its truthy or falsey value, which is technically a boolean. But if you need to a real boolean representation of a value for your expression you must convert it to a real boolean value using a double not, !!.

## Should I use double or triple equals?

Triple Equals is superior to double equals. Whenever possible, you should use triple equals to test equality. By testing the type and value you can be sure that you are always executing a true equality test.

## Should you use == or ===?

The difference between == and === is that: == converts the variable values to the same type before performing comparison. This is called type coercion. === does not do any type conversion (coercion) and returns true only if both values and types are identical for the two variables being compared.

## Is NaN function JavaScript?

JavaScript isNaN() Function

The isNaN() function determines whether a value is an illegal number (Not-a-Number). This function returns true if the value equates to NaN. Otherwise it returns false.

## What are types in JavaScript?

In Javascript, there are five basic, or primitive, types of data. The five most basic types of data are strings, numbers, booleans, undefined, and null. We refer to these as primitive data types.

## What is not in Java?

The not operator is a logical operator, represented in Java by the ! It’s a unary operator that takes a boolean value as its operand. … The not operator works by inverting (or negating) the value of its operand.

## Which is not a logical operator?

The NOT logical operator reverses the true/false outcome of the expression that immediately follows. … You can substitute ~ or ¬ for NOT as a logical operator. NOT can be used to check whether a numeric variable has the value 0, 1, or any other value. For example, all scratch variables are initialized to 0.

## What is the difference between double == and triple === equals?

Answer. While these are both comparison equality operators, the triple equals, === , is what’s called a strict equality operator while the double equals is an equality operator. … If the value is the same but the type is not, the equality will evaluate to false.

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## Why would you use === instead of ==?

Use === if you want to compare couple of things in JavaScript, it’s called strict equality, it means this will return true if only both type and value are the same, so there wouldn’t be any unwanted type correction for you, if you using == , you basically don’t care about the type and in many cases you could face …

## What is the difference between double equal to and triple equal to?

Double Equals ( == ) checks for value equality only. … On the other hand, Triple Equals ( === ) does not perform type coercion. It will verify whether the variables being compared have both the same value AND the same type.