Tag: way to remove all falsy values from an array in JavaScript.

JavaScript often surprises us with how much we can do using very little code.
One such powerful and commonly used trick is:

const arr = ["", null, undefined, false, 0, 1, 2];
const result = arr.filter(Boolean);
console.log(result);

✅ Output

[1, 2]

But why does this happen?
Let’s break it down in a simple and clear way.

What Does filter(Boolean) Mean?

The filter() method creates a new array by keeping only the elements that satisfy a condition.

This line:

arr.filter(Boolean)

is actually shorthand for:

arr.filter(value => Boolean(value))

So every element in the array is passed into the Boolean() function.

How Boolean() Works in JavaScript

The Boolean() function converts any value into either true or false.

❌ Falsy Values

These values always return false:

• "" (empty string)
• null
• undefined
• false
• 0
• NaN

✅ Truthy Values

Everything else is considered true, including:

• 1
• 2
• "hello"
• []
• {}

🔎 Step-by-Step Execution

Only truthy values survive the filter.

Final Result

[1, 2]

✨ Why Developers Love This Pattern

Using filter(Boolean):

• Removes unwanted falsy values
• Makes code shorter and cleaner
• Improves readability once understood

Instead of writing:

arr.filter(value => value !== null && value !== undefined && value !== "")

You can simply write:

arr.filter(Boolean)

⚠️ Important Thing to Remember

This method removes all falsy values, including 0 and false.

So do not use it if 0 or false are valid values in your data.

When to Use filter(Boolean)

✅ Cleaning API responses
✅ Removing empty values from arrays
✅ Simplifying data before rendering

❌ When 0 or false are meaningful values

🧠 Interview One-Liner

filter(Boolean) is a concise way to remove all falsy values from an array in JavaScript.

📌 Final Thought

Sometimes, one line of JavaScript can replace multiple lines of code —
but only if you truly understand why it works.

Happy coding 🚀

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