Javascript developer learning Ruby: Case Equality Operator

As a JavaScript developer learning Ruby, one of the most unexpected discoveries for me so far was the case equality operator (===). In JavaScript, === is all about strict equality, meaning both value and type must match:

console.log(5 === '5'); // false
console.log(5 === 5); // true

But in Ruby, === is not even about equality check. it's a cool pattern-matching tool that makes conditional logic more elegant and expressive.

How === Works in Ruby

The === operator is primarily used in case statements and allows objects to define their own custom behavior.

Ranges

(1..10) === 5  # => true
(1..10) === 15 # => false

This means 5 is within the range 1..10. One of the things I dislike about if statements in JS is that you have to repeat the variable name in every condition (e.g. if num >= 1 && num <= 10). I know, it is not the end of the world obviously, but when I see a more elegant way of doing things, I can't help but appreciate it.

Classes and Modules (Module#===): Is the object an instance of a class?

String === "hello"  # => true
Integer === "hello" # => false

Custom Behavior in Classes (#=== Overriding)

I think this is the coolest part. You can override the === method in your own classes to define custom behavior. For example, you could use it to check if an object is valid or meets certain criteria.

class EvenNumber
  def ===(num)
    num.even?
  end
end

case 4
when EvenNumber.new then puts "It's even!"
else puts "It's odd!"
end

Wrap

I am really liking so far how expressive and flexible Ruby is. Wrapping up with this;

JAVASCRIPT 👇

function classify(value) {
  if (value >= 1 && value <= 10) {
    return 'Number is between 1 and 10';
  } else if (typeof value === 'string') {
    return "It's a string!";
  } else if (/\d+/.test(value)) {
    return 'Contains a digit';
  } else {
    return 'Something else';
  }
}

RUBY 👇

def classify(value)
  case value
  when 1..10 then "Number is between 1 and 10"
  when String then "It's a string"
  when /\d+/  then "Contains a digit"
  else "Something else"
  end
end

Love this elegancy 💅