6  Arithmetic Operators

Here’s a comprehensive table of JavaScript’s arithmetic operators, along with examples and special behaviors:

Operator	Name	Description	Example	Result
+	Addition	Adds numbers	5 + 3	8
-	Subtraction	Subtracts numbers	5 - 3	2
*	Multiplication	Multiplies numbers	5 * 3	15
/	Division	Divides numbers	6 / 3	2
%	Modulus (Remainder)	Returns the division remainder	7 % 3	1
**	Exponentiation	Raises first operand to power of second	2 ** 3	8
++	Increment	Increases value by 1	let x = 5; x++;	x becomes 6
--	Decrement	Decreases value by 1	let x = 5; x--;	x becomes 4
+=	Addition assignment	Adds and assigns result	let x = 5; x += 3;	x becomes 8
-=	Subtraction assignment	Subtracts and assigns result	let x = 5; x -= 3;	x becomes 2
*=	Multiplication assignment	Multiplies and assigns result	let x = 5; x *= 3;	x becomes 15
/=	Division assignment	Divides and assigns result	let x = 6; x /= 3;	x becomes 2
%=	Modulus assignment	Performs modulus and assigns result	let x = 7; x %= 3;	x becomes 1
**=	Exponentiation assignment	Performs exponentiation and assigns result	let x = 2; x **= 3;	x becomes 8

6.1 Special Behaviors and Gotchas

The + operator has multiple behaviors in JavaScript:

1. Number addition: When both operands are numbers

   5 + 3   // 8

2. String concatenation: When either operand is a string

   "Hello" + " World"   // "Hello World"
   "The answer is " + 42   // "The answer is 42"
   42 + " is the answer"   // "42 is the answer"

3. Type coercion: JavaScript tries to convert non-string values to strings when concatenating

   "5" + 3   // "53" (number 3 coerced to string)
   5 + "3"   // "53" (number 5 coerced to string)

For other arithmetic operators, JavaScript attempts to convert strings to numbers:

"5" - 3     // 2 (string "5" coerced to number)
"5" * "3"   // 15 (both strings coerced to numbers)
10 / "2"    // 5 (string "2" coerced to number)

6.2 Increment/Decrement Position Matters

The position of the ++ and -- operators changes their behavior:

// Prefix (returns new value)
let a = 5;
let b = ++a;   // a becomes 6, b becomes 6

// Postfix (returns original value)
let c = 5;
let d = c++;   // c becomes 6, but d becomes 5

6.3 Division and Special Number Values

Division has some special cases in JavaScript:

10 / 0         // Infinity
-10 / 0        // -Infinity
0 / 0          // NaN (Not a Number)

6.4 The Math Object for More Complex Operations

For more advanced math operations, JavaScript provides the Math object:

Math.floor(5.95)     // 5 (rounds down)
Math.ceil(5.05)      // 6 (rounds up)
Math.round(5.5)      // 6 (rounds to nearest integer)
Math.abs(-5)         // 5 (absolute value)
Math.sqrt(25)        // 5 (square root)
Math.min(2, 5, 1)    // 1 (minimum value)
Math.max(2, 5, 1)    // 5 (maximum value)
Math.random()        // Random number between 0 and 1 (exclusive)

6.5 Integer Division Workaround

Unlike some languages, JavaScript doesn’t have a dedicated integer division operator. To perform integer division, you can use:

Math.floor(7 / 2)    // 3 (discards the decimal part)
~~(7 / 2)            // 3 (bitwise NOT trick for integer division)
(7 / 2) | 0          // 3 (bitwise OR with 0 for integer division)

Understanding these arithmetic operators and their behaviors is essential for writing effective JavaScript code, especially when dealing with user inputs and numeric calculations.