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TwisterRL
TwisterRL

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JavaScript’s Weirdest Comparison

#webdev #programming #javascript #beginners 
[] == false        // true
[] == ![]          // true
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Wait… what? 🤯

How can an empty array be equal to false?

Let’s break it down

JavaScript’s == operator performs type coercion.

That means it tries to convert values to the same type before comparing them.

Step 1 

[] == false
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  • false becomes 0
  • [] becomes "" (empty string)
  • "" becomes 0

So we end up with:

0 == 0  // true
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Step 2 

[] == ![]
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First evaluate ![]:

  • [] is truthy
  • ![] becomes false

So now we have:

[] == false
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Which we already know is:

true
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Why this matters

The == operator can lead to unexpected results because of implicit type conversion.

That’s why most developers prefer:

===
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It compares values without coercion.

Takeaway

JavaScript doesn’t behave randomly.
It follows rules — even strange ones.

Understand coercion, and the weirdness disappears.

Happy coding ✨

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