What is the JavaScript equivalent of Ruby's "unless"?

Question

Ruby has a handy unless conditional, which is "The negative equivalent of if."

Is there a way to do a "negative if" in JavaScript that's more semantic than if (!condition)?

Answer 1

Here's the hack :P

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

Answer 2

No, there's no such control structure. One thing you can do to make code more readable is wrap the negation in a function.

 function baconIsTooThin () {
    return !baconIsChunky();
 }

 if (baconIsTooThin()) { 
   ...
 } 

Or you may want to use CoffeeScript, which makes JavaScript look more like Ruby (and has unless) and compiles down to plain JavaScript.

Example:

// CoffeeScript
unless (foo) 
  alert('bar')

// Compiled JavaScript
if (!foo) {
 alert('bar');
}