Conditions

Make a decision

Lesson 4 of 20 · 7 min · Module 2: Decisions & reusable work

Great programs make decisions. An if statement runs a block of code only when its condition is true.

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By the end, you’ll be able to…

Evaluate a comparison
Choose between branches
Return a result from a function

The idea

Use if and else to choose between two paths. A comparison like score >= 50 produces true or false.

const temperature = 24;
if (temperature > 20) {
  console.log("T-shirt weather!");
} else {
  console.log("Grab a jacket.");
}

01Read a boolean condition

age >= 18 is either true or false. The equality boundary matters: an age of exactly 18 must take the Yes branch.

console.log(18 >= 18);
console.log(17 >= 18);

Output

true
false

02Understand the function wrapper

function canVote(age) defines reusable behavior; it does not run that behavior immediately. Calling canVote(20) supplies age = 20. return sends the chosen string back to the caller. The next module explores functions further.

Your turn

Create a function canVote(age) that returns "Yes" for ages 18 and above, and "Not yet" otherwise.

What the checks look for

Age 18 can vote
Age 16 cannot vote yet
Works with other ages

Try it in the editor →

Take this with you

A decision is correct only when its boundary cases match the intended rule.