📝 JavaScript Statements

In JavaScript, a statement is a single instruction or command that the browser interprets and executes. Statements tell the browser what to do, whether it’s calculating a value, displaying output, or controlling the flow of the program.

This tutorial will cover the types of JavaScript statements, how to use them, and some examples to help you understand their role in your code.

1. 🏁 Expression Statements

An expression in JavaScript is any valid unit of code that resolves to a value. When you put an expression inside a statement, that statement is called an expression statement.

Example:

jsCopyEditlet total = 5 + 10;  // "5 + 10" is an expression, and the whole line is a statement

Here, total = 5 + 10 is an expression statement. The expression 5 + 10 evaluates to 15, and the result is assigned to the variable total.

2. ⏳ Declaration Statements

A declaration is a statement that defines a variable or function. It’s used to create variables and functions that can be referenced later.

Example: Variable Declaration

jsCopyEditlet name = "Alice";  // Declaring a variable "name" with the value "Alice"

Here, the statement let name = "Alice" declares a variable name and assigns it the value "Alice".

Example: Function Declaration

jsCopyEditfunction greet() {
  console.log("Hello, world!");
}  // Declaring a function named "greet"

This statement defines a function greet() that, when called, will display "Hello, world!" in the console.

3. 🏁 Control Flow Statements

Control flow statements allow you to make decisions in your code or repeat tasks. These include if statements, loops, and switch statements.

Example: If-Else Statement

jsCopyEditlet age = 18;
if (age >= 18) {
  console.log("Adult");
} else {
  console.log("Minor");
}

The if statement checks the condition age >= 18 and, if true, logs "Adult" to the console. If the condition is false, it logs "Minor".

Example: For Loop

jsCopyEditfor (let i = 0; i < 5; i++) {
  console.log(i);  // Logs numbers 0 to 4
}

This loop repeats the block of code inside it, printing numbers from 0 to 4.

4. 🔄 Iteration Statements

JavaScript provides several iteration statements to perform tasks multiple times. These are typically used with loops like for, while, and do...while.

Example: While Loop

jsCopyEditlet count = 0;
while (count < 3) {
  console.log(count);
  count++;  // Increments count by 1 on each iteration
}

The while loop continues running as long as the condition count < 3 is true, printing numbers 0 to 2.

5. 🔀 Jump Statements

Jump statements allow you to control the flow of your program in more flexible ways. These include break, continue, and return.

Example: Break Statement

jsCopyEditfor (let i = 0; i < 10; i++) {
  if (i === 5) {
    break;  // Exits the loop when i is 5
  }
  console.log(i);
}

In this example, the loop stops as soon as i reaches 5 due to the break statement.

Example: Return Statement

jsCopyEditfunction add(x, y) {
  return x + y;  // Exits the function and returns the result
}

The return statement exits the function and returns a value.

6. 🎯 Empty Statement

An empty statement is a statement that does nothing. It’s usually represented by a semicolon ;.

jsCopyEdit;  // This is a valid, but empty statement

Empty statements are rare, but they might be used in cases where you need a placeholder.

✅ Summary of Common JavaScript Statements

🎯 Final Tips:

• Statements are the building blocks of your code. They determine what happens when the program runs.
• Start with declarations and expression statements, then move on to control flow and iteration statements as you build more complex programs.
• Always practice using statements to better understand how control flows through your program.