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..'