Zero Bit In Javascript

In JavaScript, a variable representing a "zero bit" means it holds no set bits, which is simply the number 0. Here’s how you can work with such a variable and manipulate it effectively:

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Initializing a Zero-Bit Variable

You can declare and initialize a variable with 0:

let zeroBit = 0;

This variable has all bits unset.

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Checking if a Variable Has Zero Bits

You can check if a number has no set bits using:

if (zeroBit === 0) {
    console.log("This variable has zero bits set.");
}

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Setting a Bit in the Variable

You can set a specific bit in the zero-bit variable:

let bit = 2; // Example: Setting the 2nd bit
zeroBit = zeroBit | (1 << bit);
console.log(zeroBit.toString(2)); // Output: "100"

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Unsetting Bits

If the variable starts as 0, all bits are already unset, so unsetting won't change it. But here’s how you can do it:

zeroBit = zeroBit & ~(1 << 2); // This would still result in 0
console.log(zeroBit.toString(2)); // Output: "0"

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Using Zero-Bit Variable in Functions

For instance, if you’re working with a function that manipulates bits, you can use the zero-bit variable as the starting point:

function createNumberWithSetBits(bitPositions) {
    let num = 0; // Start with a zero-bit variable
    for (let bit of bitPositions) {
        num = num | (1 << bit);
    }
    return num;
}

// Example usage:
let result = createNumberWithSetBits([0, 2, 4]); // Sets bits 0, 2, and 4
console.log(result.toString(2)); // Output: "10101"

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Example: Working with Zero-Bit Variable

Here’s how you might use a zero-bit variable to construct a number with exactly n set bits:

function createNumberWithNBits(n) {
    let num = 0; // Start with zero bits
    for (let i = 0; i < n; i++) {
        num = num | (1 << i); // Set the i-th bit
    }
    return num;
}

// Example: Create a number with 3 set bits
console.log(createNumberWithNBits(3).toString(2)); // Output: "111"

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Key Operations for Zero-Bit Variable

1. Set a bit: num = num | (1 << bit)

2. Unset a bit: num = num & ~(1 << bit)

3. Toggle a bit: num = num ^ (1 << bit)

4. Check if a bit is set: (num & (1 << bit)) !== 0