In JavaScript, not is an operator that can be used to negate a boolean value, meaning it will invert true to false or false to true.
The syntax for using the not operator is to place an exclamation point before the expression you want to negate.
Here are a few examples:
1. Negating a boolean value:
let a = true;
let b = !a; // b is now false
2. Checking if a variable is not equal to a certain value:
let age = 18;
if (age !== 21) {
console.log("You are not old enough to drink");
}
// Output: You are not old enough to drink
3. Evaluating if a value is not truthy:
In JavaScript, the values null, undefined, 0, false, NaN, and ''(empty string) are considered falsey.
let value = null;
if (!value) {
console.log("The value is not truthy");
}
// Output: The value is not truthy
By using the not operator, you can easily flip boolean values, check for inequality, and check for falsey values.