Once upon a time, in the digital kingdom, there was a mischievous wizard named Tilde. Tilde loved going into rooms full of glowing switches—some ON (1), some OFF (0). But he had only one rule: 👉 He flipped every single switch he saw.

  • If a switch was ON (1), he turned it OFF (0).
  • If a switch was OFF (0), he turned it ON (1).

This magical flipping is exactly what the tilde operator (~) does in JavaScript.

What Does ~ Do?

The tilde is a bitwise NOT operator.

  • It looks at every bit (1s and 0s) of a number.
  • Then it flips them: 1 → 0, 0 → 1.

Example:

let x = 5;      // 00000101 in binary
console.log(~x); // 11111010 in binary → -6

Whoa! How did 5 become -6? That’s because in computers, negative numbers are stored in a special binary format called two’s complement. When you flip all the bits of 5, you actually get -6.

So What’s the Use of ~?

Even though it seems strange, the tilde has some clever uses:

  1. Quickly turn positives into negatives (and vice versa).

    • ~x is basically the same as -(x + 1).

  2. Check if a number is NOT found in a list.

    • For example, in old-school coding, indexOf returns -1 if something isn’t found.
    • Using ~index was a clever shortcut to check this.

Example:

let fruits = ["apple", "banana", "mango"];
console.log(~fruits.indexOf("banana")); // Not -1 → true
console.log(~fruits.indexOf("grape"));  // -1 → 0 → false

Real-Life Analogy

Think of Tilde as a prankster who sneaks into a classroom with light switches.

  • If the light is ON, he turns it OFF.
  • If the light is OFF, he turns it ON. The room looks completely opposite after he’s done—just like numbers after applying ~.

In Short

  • ~ = Bitwise NOT operator.
  • Flips all bits: 1 → 0, 0 → 1.
  • ~x equals -(x + 1).
  • Useful in quick tricks like checking indexOf.

Review Questions

  1. The tilde (~) operator is also called the __________ NOT operator.
  2. The tilde flips every __________ of a number.
  3. If a bit is 1, tilde turns it into __________.
  4. If a bit is 0, tilde turns it into __________.
  5. In binary, 5 (00000101) becomes __________ after applying ~.
  6. ~x is the same as __________ in math form.
  7. indexOf() returns __________ when an item is not found in an array.
  8. Using ~index is a coding shortcut for checking if something is __________.
  9. A real-life analogy for tilde is a prankster flipping all the __________ in a classroom.
  10. The tilde operator is written as the symbol __________.
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