JavaScript Operators and Expressions

What Are Operators and Expressions?

In JavaScript, an expression is any valid combination of variables, values, and operators that results in a value.

An operator is a symbol that performs a specific operation on one or more values (called operands).

Example:

let sum = 10 + 5; // '+' is an operator; '10 + 5' is an expression

Arithmetic Operators

These are used to perform basic mathematical operations.

Example:

let x = 10;
x++;     // 11
x *= 2;  // 22

Assignment Operators

These assign values to variables.

Example:

let a = 10;
a += 5; // a is now 15

Comparison Operators

These are used to compare two values and return a Boolean result (true or false).

Tip:
Use === and !== instead of == and != to avoid unexpected type coercion.

Logical Operators

Used to combine multiple boolean expressions.

Example:

let age = 25;
let isAdult = age >= 18 && age < 60; // true

Bitwise Operators (Advanced, Use Rarely)

These work on numbers at the binary level.

Note: Bitwise operators are rarely used in beginner-level JavaScript but useful in performance-critical or system-level programming.

Ternary Operator

A shorthand for if...else.

Syntax:

condition ? expressionIfTrue : expressionIfFalse;

Example:

let age = 18;
let status = age >= 18 ? "Adult" : "Minor"; // "Adult"

This is very useful for quick value decisions.

Operator Precedence

When multiple operators appear in one expression, JavaScript follows a specific order of operations (just like math).

For example:

let result = 10 + 5 * 2; // 20 (not 30)

Explanation:
Multiplication (*) has higher precedence than addition (+), so 5 * 2 happens first.

Common Precedence Order:

1. () — Parentheses
2. ** — Exponentiation
3. * / % — Multiplication, Division, Modulus
4. + - — Addition, Subtraction
5. Comparison (<, >, ==, etc.)
6. Logical (&&, ||)
7. Assignment (=, +=, etc.)

Use parentheses to control and clarify complex expressions:

let result = (10 + 5) * 2; // 30

Summary

• Use arithmetic operators for math (+, -, *, /).
• Use assignment operators (=, +=, -=) to set or update values.
• Use comparison operators (===, >, <) to compare values.
• Use logical operators (&&, ||, !) in conditional expressions.
• Use the ternary operator for quick if...else alternatives.
• Know operator precedence to avoid bugs in complex expressions.