JavaScript Operators

1// Basic arithmetic
2let a = 10;
3let b = 3;
4
5let sum = a + b;          // 13
6let difference = a - b;   // 7
7let product = a * b;      // 30
8let quotient = a / b;     // 3.3333...
9let remainder = a % b;    // 1
10let power = a ** b;       // 1000 (10 to the power of 3)
11
12// Increment and decrement
13let count = 0;
14count++;                  // count is now 1
15count--;                  // count is back to 0
16
17// Pre vs Post increment
18let x = 5;
19let y = x++;              // y = 5, x = 6
20let z = ++x;              // x = 7, z = 7
21
22// With strings
23let greeting = "Hello " + "World";  // "Hello World"

1// Assignment operators
2let score = 10;
3
4score += 5;     // score is now 15 (10 + 5)
5score -= 3;     // score is now 12 (15 - 3)
6score *= 2;     // score is now 24 (12 * 2)
7score /= 4;     // score is now 6 (24 / 4)
8score %= 4;     // score is now 2 (6 % 4)
9score **= 3;    // score is now 8 (2 ** 3)
10
11// With strings
12let greeting = "Hello";
13greeting += " World"; // greeting is now "Hello World"

1// Comparison operators
2let a = 5;
3let b = "5";
4let c = 10;
5
6// Equality
7console.log(a == b);    // true (values are equal, ignores type)
8console.log(a === b);   // false (different types)
9console.log(a != c);    // true (values are not equal)
10console.log(a !== b);   // true (different types)
11
12// Relational
13console.log(a > 3);     // true (5 is greater than 3)
14console.log(a < c);     // true (5 is less than 10)
15console.log(a >= 5);    // true (5 is greater than or equal to 5)
16console.log(a <= 4);    // false (5 is not less than or equal to 4)
17
18// Common use case: conditionals
19if (a === 5) {
20  console.log("a is exactly 5");
21}
22
23if (c > a) {
24  console.log("c is greater than a");
25}

1// Logical operators
2let isLoggedIn = true;
3let hasPermission = false;
4
5// Logical AND: both must be true
6if (isLoggedIn && hasPermission) {
7  console.log("You can access the admin panel");
8} else {
9  console.log("Access denied"); // This will run
10}
11
12// Logical OR: at least one must be true
13if (isLoggedIn || hasPermission) {
14  console.log("You have some level of access"); // This will run
15}
16
17// Logical NOT: inverts the value
18if (!hasPermission) {
19  console.log("You don't have permission"); // This will run
20}
21
22// Combining logical operators
23let isAdmin = true;
24let isOwner = false;
25
26if ((isAdmin || isOwner) && isLoggedIn) {
27  console.log("Welcome to the control panel"); // This will run
28}

1// Short-circuit with &&
2// If the first value is false, the second won't be evaluated
3let result1 = false && someFunction();  // someFunction is never called
4
5// Short-circuit with ||
6// If the first value is true, the second won't be evaluated
7let result2 = true || someFunction();   // someFunction is never called
8
9// Practical examples:
10
11// Set default values
12let username = userInput || "Guest";  // If userInput is empty/falsy, use "Guest"
13
14// Call a function only if a condition is met
15isLoggedIn && showDashboard();  // Only call showDashboard if isLoggedIn is true
16
17// Checking for null before accessing properties
18let user = null;
19let userName = user && user.name;  // Prevents "Cannot read property 'name' of null"

1// String concatenation with +
2let firstName = "John";
3let lastName = "Doe";
4let fullName = firstName + " " + lastName;  // "John Doe"
5
6// String concatenation with +=
7let greeting = "Hello";
8greeting += " World";  // "Hello World"
9
10// Template literals (modern way)
11let age = 30;
12let message = `${firstName} is ${age} years old`;  // "John is 30 years old"
13
14// Comparing strings
15console.log("apple" < "banana");  // true (alphabetically, "a" comes before "b")
16console.log("apple" === "Apple");  // false (case-sensitive comparison)
17console.log("apple".toLowerCase() === "Apple".toLowerCase());  // true (case-insensitive)

1// Syntax: condition ? valueIfTrue : valueIfFalse
2
3// Instead of:
4let message;
5if (age >= 18) {
6  message = "You can vote";
7} else {
8  message = "Too young to vote";
9}
10
11// You can write:
12let age = 20;
13let message = age >= 18 ? "You can vote" : "Too young to vote";
14
15// Nested ternary operators (use carefully, can reduce readability)
16let greeting = hour < 12 ? "Good morning" : hour < 18 ? "Good afternoon" : "Good evening";
17
18// Ternary with functions
19let canAccess = userRole === "admin" ? getAdminContent() : getRegularContent();

1// typeof operator
2console.log(typeof "hello");     // "string"
3console.log(typeof 42);          // "number"
4console.log(typeof true);        // "boolean"
5console.log(typeof undefined);   // "undefined"
6console.log(typeof null);        // "object" (this is a known JavaScript bug)
7console.log(typeof {});          // "object"
8console.log(typeof []);          // "object" (arrays are objects in JavaScript)
9console.log(typeof function(){}); // "function"
10
11// instanceof operator (checks if an object is an instance of a class)
12let arr = [1, 2, 3];
13console.log(arr instanceof Array);  // true
14
15let date = new Date();
16console.log(date instanceof Date);  // true
17
18// Better way to check for arrays
19console.log(Array.isArray(arr));    // true
20console.log(Array.isArray({}));     // false

1// Bitwise operators (work on binary representation of numbers)
2let a = 5;      // binary: 101
3let b = 3;      // binary: 011
4
5console.log(a & b);    // Bitwise AND: 1 (binary: 001)
6console.log(a | b);    // Bitwise OR: 7 (binary: 111)
7console.log(a ^ b);    // Bitwise XOR: 6 (binary: 110)
8console.log(~a);       // Bitwise NOT: -6
9console.log(a << 1);   // Left shift: 10 (binary: 1010)
10console.log(a >> 1);   // Right shift: 2 (binary: 10)

1// Operator precedence examples
2let result = 2 + 3 * 4;    // 14, not 20 (multiplication happens first)
3let result2 = (2 + 3) * 4; // 20 (parentheses override default precedence)
4
5// Multiple operators
6let x = 5;
7let y = 10;
8let z = 15;
9
10let result3 = x + y * z;             // 155
11let result4 = x + y > z && z > y;    // false (comparison happens before logical AND)
12
13// When in doubt, use parentheses for clarity
14let result5 = (x + y) > z && (z > y); // false, but clearer intention