In JavaScript - ECMAScript 2021, unless is not a valid keyword or operator. However, you can achieve a similar logic using an if statement with a negated condition. The if statement will execute its code block only when the condition is false.
Here's an example of using unless logic with an if statement:
let x = 10;
if (!(x > 20)) {
console.log("x is not greater than 20");
}
In this example, the code inside the if statement block will execute only if x is not greater than 20. Therefore, the statement "x is not greater than 20" will be logged to the console.
Another example:
let y = 5;
if (!(y === 10)) {
console.log("y is not equal to 10");
}
In this example, the code inside the if statement block will execute only if y is not equal to 10. Therefore, the statement "y is not equal to 10" will be logged to the console.
In both cases, the if statement is used with a negated condition, which is equivalent to using unless. This logic can be useful for simplifying code and avoiding nested if-else statements.