Why 0.1 + 0.2 ≠ 0.3 in JavaScript

The Mind-Blowing Truth

Wait, what?! Math is broken in JavaScript? Not quite - but close enough to ruin your day!

Why JavaScript "Can't Do Math"

🎯 The Real Culprit: IEEE 754 Binary Floating-Point Standard

Think of it like this:

• Decimal system (humans): We count in base 10 (0,1,2,3,4,5,6,7,8,9)
• Binary system (computers): Computers count in base 2 (0,1)

Some decimal numbers can't be perfectly represented in binary, just like 1/3 can't be perfectly written as a decimal (0.333333... forever).

The Binary Translation Problem

It's like trying to fit an infinite number into a finite box !

When you perform 0.1 + 0.2 in JavaScript, the internal representation of these approximations are added together. The result is not exactly 0.3, but a value very, very close to it, such as 0.30000000000000004. Because of this tiny discrepancy, a strict equality comparison (===) with 0.3 will fail.

Real-World Examples :

🧮 Calculator Errors

💰 Financial Calculations

The Fixes

To mitigate this problem, especially when comparing floating-point numbers, you should avoid using strict equality (===) directly. Instead, employ a tolerance check or a threshold value (often called an epsilon`).

This involves checking if the absolute difference between the two numbers is less than a very small predefined value.

🏆 Method 1: Tolerance Checking (Epsilon)

💡 Method 2: Number.EPSILON (Built-in Tolerance)

Quick Memory Tricks

🧠 Remember: "Floats float away from accuracy"

🎯 Rule: Never use === with decimal numbers in JavaScript 💡

Solution: Always use tolerance when comparing floats

Languages That Have This Problem

• JavaScript ✅
• Python ✅
• Java ✅
• C++ ✅

It's not a bug, it's a feature! 😅 (Actually, it's just how computers work)

Understanding these nuances of floating-point arithmetic is crucial for writing robust and accurate JavaScript applications, especially when dealing with numerical data.