Using not (!) inside "if" statement in JS [SOLVED]

Introduction

There are different ways to phrase conditional logic. If we have a certain condition, let’s do this, else, let’s do that. This is the typical logic that guides conditional logic, and basically the if/else statement. However, we can always expand the way we work around the if/else statement with other Boolean operators such as not, and, etc.

To negate code in JavaScript, we can make use of the JavaScript logical NOT or Negate (!) operator, and in this article, we will discuss how to achieve this and write if not code.

 

The NOT (!) operator

The NOT (!) operator, when applied on an operand, reverses the Boolean value. For example, it changes true to false, and vice-versa. It is considered a negation.

Let’s see the NOT operator at work

console.log(!false);
console.log(!(13 > 10));

Output

true
false

The first log statement shows the NOT operator reversing the false value to true. In the second log statement, the comparison statement is first executed to true, and then the NOT operator reverses the true value to false.

 

Using if not for conditional logic

In conditional logic, we can make use of logical operators such as the NOT operator. So in certain scenarios, we might need to negate the condition for a simpler code. Therefore, with the use of the NOT operator, we can negate the if statement.

For example, we write a code to check if isActive is true, log active, and log not active, if otherwise.

let isActive = true;

if (isActive) {
    console.log("active");
} else {
    console.log("not active");
}

Output

active

However, if we only need to log a not active statement and not the active statement. So there is no way for us to log the not active without having to change the conditional logic. That’s where a if not statement comes in. With a if not statement, we will not need to have a else statement. Then, the NOT operator negates the isActive Boolean value to false which is the condition for the not active statement.

let isActive = true;

if (!isActive) {
    console.log("not active");
}

Output

not active

 

Summary

If you want to negate a if statement, we can do so using the NOT operator which reverses the Boolean value, and so changes it from true to false or from false to true.

 

References

Logical NOT (!) - JavaScript | MDN (mozilla.org)
How to negate code in "if" statement block in JavaScript -JQuery like 'if not then..'