Equivalent of Ruby unless Statement in JavaScript

1. Create a User-Defined Function to Implement the unless Statement in JavaScript
2. Negate the if-else Statement to Implement the unless Statement in JavaScript

In Ruby, the conditional statements follow the unless convention, whereas most programming languages prefer the if-else condition. The benefit is similar; just the preference is in-built with each language.

Other than Ruby, Perl, CoffeeScript, etc., use the unless statement.

Here, in our case, we will visualize the application of a general if-else statement with the definition of unless. This means we will configure our if-else statement to behave like an unless statement.

For the drive, we will generate a function called unless, and also, we will use direct if-else to perform the unless statement’s operation.

Create a User-Defined Function to Implement the unless Statement in JavaScript

The function we will create here will take on a condition. Also, based on that condition, we will generate another callback function that will infer the function’s satisfiability.

Let’s see the code lines for a better understanding.

Code Snippet:

let unless = (condition, callback) => {
  !condition && callback();
} let a = 10;
let b = 20;
unless(a > b, () => {console.log('A should be greater than B')})

Output:

As you can see, the function unless takes a condition. In our case, the condition is that a is less than b.

But the unless function is negated, and when we set the condition as a>b, it will accept it and trigger the callback function to operate. But according to the scenario of a general if-else statement, it was not supposed to trigger the callback function as the condition would have fallen under the else statement.

Negate the if-else Statement to Implement the unless Statement in JavaScript

This part is comparatively easier to grasp and implement. All you need is to set the if work like else and the else work like if.

Whatever condition is applied on if will be negated beforehand, and thus, the else will be automatically defined. Let us try the code fence to demonstrate the situation.

Code Snippet:

var a = 42;
var b = 10;
if (!(a > b)) {
  console.log('Incorrect');
} else {
  console.log('Correct');
}

Output: