JavaScript Fundamentals: Loops and Conditionals Explained

The core logic building blocks for every program you write.

Welcome! When you write code, you need a way to make decisions and perform repetitive tasks. In **JavaScript**, these two actions are controlled by **conditional statements** and **loops**. Mastering these two concepts is the absolute foundation of writing functional, dynamic, and efficient programs.

Part 1: Conditional Statements (Making Decisions)

Conditional statements allow your code to execute different blocks of logic based on whether a condition is true or false. The most common form is the **`if/else`** structure.

The `if/else` Statement

This structure evaluates a condition inside the parentheses. If the condition is `true`, the code inside the `if` block runs. If it's `false`, the code inside the `else` block (if present) runs.

let temperature = 25;

if (temperature > 30) {
  console.log("It's a hot day!");
} else if (temperature >= 20) {
  console.log("It's a pleasant day.");
} else {
  console.log("It's a cold day.");
}
            

Part 2: Loops (Doing Things Repeatedly)

Loops are used to execute a block of code a specific number of times, or as long as a certain condition remains true. This saves you from writing the same code over and over again.

The `for` Loop

The `for` loop is the most common loop. It requires three things: a starting point (initialization), a condition that must be true for the loop to continue, and an increment/decrement step.

// Example: Counting from 1 to 5
for (let i = 1; i <= 5; i++) {
  console.log(i);
}
// Output: 1, 2, 3, 4, 5
            

The `while` Loop

The `while` loop is simpler: it keeps running as long as a specified condition is true. Be careful not to create an **infinite loop** (where the condition never becomes false!).

let counter = 0;

while (counter < 3) {
  console.log("Running...");
  counter++; // Important: This prevents the infinite loop!
}
// Output: Running... (x3)
            By using `if/else` to make decisions and `for/while` to automate repetition, you gain complete control over how your JavaScript programs execute.

        

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