2-conditionals

Like humans, computer programs make decisions based on information given to them. Conditionals are a way of representing these decisions in code.

For example:

• In a game, if the player has 0 lives, then the game is over
• In a weather app, if rain is forecast, a picture of rain clouds is shown

The most common type of conditional is the if statement.

An if statment runs some code if a condition is met. If the condition is not met, then the code will skipped.

var isHappy = true;

if (isHappy) {
  console.log("I am happy");
}

The code in paratheses - e.g. (isHappy) - is the condition. The condition can be any expression. The following are all valid conditions:

// boolean value
if (true) {
  // do something
}

// variable assigned to boolean value
if (isHappy) {
  // do something
}

// equality operator returns a boolean value
if (1 + 1 === 2) {
  // do something
}

// comparison operator returns a boolean value
if (10 > 5) {
  // do something
}

// function call returns boolean value
if (greaterThan10(5)) {
  // do something
}

An if statement runs code when a condition is met. What if the condition is not met? Sometimes you want to run an alternative bit of code.

An if...else statement also runs code when the condition is not met.

var isHappy = true;

if (isHappy) {
  console.log("I am happy 😄");
} else {
  console.log("I am not happy 😢");
}