Javascript Bitwise Operators

What is a Bitwise Operator in JavaScript?

Some programming languages allow operations to be performed directly on the binary representations of numbers. JavaScript is one of these languages, and Bitwise Operators are the tools that carry out these operations.

In JavaScript, bitwise operators fall into three categories: bitwise logical operators, shift operators, and the bitwise NOT operator. Here are a few examples of what these operators are and how they operate:

var a = 3; // binary: 0011
var b = 5; // binary: 0101

console.log(a & b); // 1 => binary: 0001
console.log(a | b); // 7 => binary: 0111
console.log(~a); // -4 => binary: 1100
console.log(a ^ b); // 6 => binary: 0110

Basic Definition of Bitwise Operators in JavaScript

A basic understanding of Bitwise Operators in JavaScript requires knowledge of binary numbers and the logic gates that manipulate them. A bitwise operator treats their operands as a sequence of 32 bits, rather than as decimal, hexadecimal, or octal numbers. From a numeric perspective, these operators always return a number, even if the entering parameters are not numbers.

Importance of Bitwise Operators in JavaScript

You might be questioning, why do we need to manipulate bits in JavaScript? Is it of any consequence? You'd be correct in asking these questions, and the answer is that it's unique to every situation. Despite being infrequently utilised in JavaScript, Bitwise Operators have their applications, primarily when engaged with lower-level programming, encryption, and dealing with hardware.

JavaScript Bitwise Operators: Common Examples

There's no better way to understand the working of JavaScript Bitwise Operators than by using practical examples. This method can help you relate abstract concepts to more tangible, concrete operations. Here, we'll delve into some common examples for the Bitwise AND, OR, and NOT operators.

JavaScript Bitwise And Operator: An Example

The JavaScript Bitwise AND Operator, denoted by &, operates on two 32-bit values; it returns a new integer wherein each bit has a value of 1 only if both corresponding bits in the original integers have values of 1. Otherwise, it returns 0.

Consider two variables, 'a' and 'b', with given values:

var a = 9;  // binary: 1001
var b = 12; // binary: 1100

Let's delve into the operation \(a \& b\) using a binary perspective:

• 1st bit: 1 (from 'a') and 1 (from 'b') equals 1
• 2nd bit: 0 (from 'a') and 1 (from 'b') equals 0
• 3rd bit: 0 (from 'a') and 0 (from 'b') equals 0
• 4th bit: 1 (from 'a') and 1 (from 'b') equals 1

From the operations, we obtain a binary result of 1000 which in decimal format equals to 8. Therefore, \(a \& b\) equals 8.

JavaScript Bitwise Or Operator: An Example

The Bitwise OR Operator in JavaScript, represented by |, operates on two 32-bit values; it returns a new integer in which each bit is set to 1 if either of the corresponding bits in the original integers is 1. If both are 0, it returns 0.

Again, let's consider the variables 'a' and 'b'

var a = 9;  // binary: 1001
var b = 12; // binary: 1100

Let's write out the operation \(a | b\) in binary:

• 1st bit: 1 (from 'a') or 1 (from 'b') equals 1
• 2nd bit: 0 (from 'a') or 1 (from 'b') equals 1
• 3rd bit: 0 (from 'a') or 0 (from 'b') equals 0
• 4th bit: 1 (from 'a') or 1 (from 'b') equals 1

From these individual operations, we get a binary outcome of 1101, equivalent to the decimal number 13. Hence, \(a | b\) equals 13.

JavaScript Bitwise Not Operator: An Example

The Bitwise NOT Operator, expressed by ~ in JavaScript, conducts a negation operation on a 32-bit value, flipping every bit in the binary representation of the value.

For example, suppose we have a variable 'a':

var a = 9;  // binary: 1001

Applying the Bitwise NOT Operator would work as follows:

• 1st bit: Not 1 (from 'a') is 0
• 2nd bit: Not 0 (from 'a') is 1
• 3rd bit: Not 0 (from 'a') is 1
• 4th bit: Not 1 (from 'a') is 0

Consequently, we get a binary result of 0110, which is equivalent to the decimal number -10. This is due to the representation of negative numbers in binary format (Two's complement), where the leftmost bit works as a sign bit. Consequently, \(\sim a\) gives us -10.

Special JavaScript Bitwise Operators

In addition to the fundamental bitwise operators, JavaScript features special bitwise operators that permit unique manipulations at the bit level. Two such intriguing operators are the Bitwise Left Shift Operator and Bitwise NOT Operator. Their distinctiveness stems from how they manipulate bits to yield surprising and remarkably useful results.

Bitwise Left Shift Operator in JavaScript

Apart from basic bitwise operators in JavaScript, there's a particular category known as shift operators. One of these is the Bitwise Left Shift Operator, denoted by <<. This operator facilitates a roll-over of bits from one side of a binary number to the other, essentially 'shifting' bits to the left.

For instance, consider a binary number 1011 (which equals 11). If one uses the Bitwise Left Shift Operator on this number, shifting it to the left by two positions, it becomes 101100 (or 44 in decimal format).

Usage and Role of Bitwise Left Shift Operator in JavaScript

The Bitwise Left Shift Operator demonstrates remarkable properties regarding efficiency and resource optimisation in JavaScript. In usage scenarios, it's impressive in performing arithmetic shifts, multiplying or dividing integers by powers of two.

var a = 5;   // binary: 101
console.log(a << 1);    // 10 => binary: 1010 => 5 * 2^1
console.log(a << 2);    // 20 => binary: 10100 => 5 * 2^2

As outlined in the above examples, the Bitwise Left Shift Operator not only shifted the bits in 'a' but simultaneously multiplied 'a' by respective powers of two.

The Bitwise Left shift operator thus plays a remarkable role, especially when dealing with large data sets requiring computation. In such scenarios, using this operator may significantly enhance the speed of calculations.

Bitwise Not Operator in JavaScript

Among other Bitwise Operators, the Bitwise NOT Operator, denoted by ~, deserves a special mention. It differs from other operators by performing a unary operation, meaning it operates on a single operand.

Visually, if you have an integer represented in binary as 1011 (or, 11 in decimal), the Bitwise NOT Operator flips each bit, yielding 0100, a binary form of -12 in JavaScript's Two's complement binary format.

Insight into the Bitwise Not Operator in JavaScript

As a unique operator, the Bitwise NOT Operator benefits programmers with its excellent capability to quickly invert a number or check for values. There's an interesting use-case of this operator in JavaScript related to finding the floor value (rounding down) of a positive number.

console.log(~-5);           // 4
console.log(~~5.9999);      // 5
console.log(Math.floor(5.9999));      // 5 (has the same output, but slower)

As the examples illustrate, the Bitwise NOT Operator is a handy, faster alternative to Math.floor for getting the floor value of a number. It's noteworthy, however, that this trick only works with positive numbers and may give incorrect results for negative input or input larger than 2147483647.

So, the Bitwise NOT Operator showcases its importance in JavaScript for quick manipulations, inverting numbers, and achieving faster, memory-efficient calculations. However, it should be used with caution, given its specific properties and restrictions.

Javascript Bitwise Operators Technique

As an integral aspect of JavaScript, Bitwise Operators offer a robust technique for handling binary data at the lowest level—individual bits. These operators operate directly on the binary data, making them a potent tool for efficient calculations and manipulations. It's essential to grasp how to effectively use these operators, which includes understanding their syntax and recognising the inherent complexities of bitwise operations.

Syntax for JavaScript Bitwise Operators

The syntax of JavaScript Bitwise Operators is noteworthy for its simplicity and ease of use. Intuitive and straightforward, the operators typically require two operands: one on the left and another on the right.

Given its straightforwardness, the syntax can be fairly simple to pick up. However, using it properly requires a reasonable grasp of binary operations and unary operations where applicable, such as for the Bitwise NOT operator.

Proper Use of Syntax in JavaScript Bitwise Operators

While the syntax of JavaScript Bitwise Operators is straightforward, using it appropriately is key to harnessing their power. It's vital to understand the kind of binary data that each operator expects and the results that they generate.

For instance, Bitwise AND (&) and OR (|) operators require two operands. They perform an operation on each bit of the binary representations of the operands. However, Bitwise NOT (~), a unary operator, works on a single operand and changes every 0 to 1 and vice versa.

All these operators return a 32-bit integer. Understanding this fact is crucial, especially when you're dealing with large numbers or negative values, which JavaScript represents using two's complement binary format.

Here's an illustrative code example showing the proper use:

var a = 13;      // binary: 1101
var b = 9;       // binary: 1001

console.log(a & b);      // 9 => binary: 1001 (Bitwise AND)
console.log(a | b);      // 13 => binary: 1101 (Bitwise OR)
console.log(~a);         // -14 => binary: 11111111111111111111111111110010 (Bitwise NOT)

Therefore, you can extensively leverage the syntax of JavaScript Bitwise Operators by understanding the nature of binary numbers and the operation of each operator, while also being mindful of JavaScript's binary format for negative numbers and large integers.

Complexity of JavaScript Bitwise Operations

Being more low-level than other programming constructions, JavaScript Bitwise Operators can introduce complexities that may be intriguing. For instance, the Bitwise Left Shift Operator doesn't simply shift bits to the left. As a matter of fact, it changes the value of an integer. It multiplies the integer by a power of 2, depending on the number of shifted positions.

Another complexity that you may encounter involves the Bitwise NOT Operator. Unlike other operators, it alters the sign of the number and subtracts one. This operator's trickiness lies in JavaScript's binary format for negative numbers, and therefore the outcome is often unexpected to users unfamiliar with this concept.

Complexity also arises through the use of JavaScript Bitwise Operators in memory-efficient and faster calculations. While these operations are internally faster than their mathematical counterparts, careless use can lead to uneasy debugging and undesired results, especially when dealing with negative values or numbers larger than 32 bits.

Overcoming the Complexities of JavaScript Bitwise Operations

The complexities of JavaScript Bitwise Operations represent a challenge. Still, with careful understanding and practice, you can start harnessing them to your advantage.

To begin with, you need to have a good grasp of the binary numbering system. This is crucial for understanding the behaviour and result of each operator. For instance, understanding how negative numbers and integers larger than 32 bits are represented in JavaScript can help make sense of the surprising outputs from certain operations, like Bitwise NOT and shifts.

Here are some recommendations:

• Use comments in the code to assist with debugging and improve the code's legibility.
• Keep results within the 32-bit limit to prevent overflowing and unexpected results.
• Avoid using Bitwise Operators with negative numbers unless you're confident with the two's complement format.
• When using shift operators, avoid shifting by 32 or more positions as JavaScript brings the shift count modulo 32.

To illustrate, have a look at the revised code example considering these best practices:

var a = 13;      // binary: 1101
var b = 9;       // binary: 1001

console.log(a & b);      // 9 => binary: 1001 (Bitwise AND)
console.log(a | b);      // 13 => binary: 1101 (Bitwise OR)
console.log(~a);         // -14 => binary: 11111111111111111111111111110010 (Bitwise NOT)
// using shift operator within the limit
console.log(a << 3);

Therefore, by understanding the binary number system, using best practices and carefully managing the complexities, you can harness the power of JavaScript Bitwise Operators while avoiding common pitfalls.