Why Does `0.5 | 0` Evaluate to 0 in JavaScript?

Exploring the Bitwise Operation in JavaScript: The Curious Case of ""|"

In JavaScript, the single pipe character ""|"" represents the bitwise or operation. This operator performs a logical evaluation on the binary representations of its operands and outputs a binary value with bit positions set to 1 if either operand has a corresponding bit set to 1.

To understand how this operator works, let's consider an example:

<code class="js">console.log(0.5 | 0); // 0
console.log(-1 | 0); // -1
console.log(1 | 0); // 1</code>

Surprisingly, 0.5 | 0 evaluates to 0, while -1 | 0 and 1 | 0 both return their input integers. This behavior arises because JavaScript's bitwise operations only operate on integers. When 0.5 is passed to the | operator, it is truncated to 0, leaving us with 0 | 0, which results in 0.

In contrast, both -1 and 1 are integers. The bitwise or operation sets the corresponding bits to 1 if either operand has that bit set. Since both -1 and 1 have all their bits set to 1, the operation simply returns the input integers: -1 | 0 returns -1, and 1 | 0 returns 1.

In essence, the single pipe operator performs a bitwise or operation, which sets bits to 1 if either input has a corresponding bit set to 1. However, since bitwise operations only apply to integers, JavaScript truncates non-integer operands, potentially altering the output of the operation.

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