The Default Greeting

Let's practice using the binary Logical OR || to provide a "fallback" value. This is its most common use case for this operator.

Write a function greet(name) that takes a single name string as an argument.

• If a name is provided (e.g., "Alice"), it should return "Hello, Alice!".

• If the name is not provided (it will be undefined) or if it's an empty string (""), it should return "Hello, Guest!".

Constraint: You cannot use an if statement for this.

Test Cases:

• greet("Alice") should return "Hello, Alice!"

• greet("") should return "Hello, Guest!"

• greet(undefined) should return "Hello, Guest!"

💡 The 'Syntax Nudge'

This is the perfect place to use the Logical OR (||) operator.

Remember its core rule: valueA || valueB The JavaScript engine first looks at valueA.

• If valueA is "truthy" (any string with content, any number not 0, true, objects, arrays), it just returns valueA and stops.

• If valueA is "falsy" (specifically undefined, null, "" (empty string), 0, false, NaN), it discards it and returns valueB instead.

We can think of operators in terms of how many "things" (we call them operands) they work on.

• Unary Operator: Works on one thing.

  • ! (Logical NOT): !isReady (flips isReady from true to false)

  • typeof: typeof 10 (tells you the type is "number")

  • i++ (Increment): Works on the single variable i.

• Binary Operator: Works on two things. This is most of what you use every day.

  • 1 + 2 (The + works on 1 and 2)

  • x > y (The > works on x and y)

  • a && b (Logical AND)

  • a || b (Logical OR - the one that confused you!)

• Ternary Operator: The one and only! It works on three things.

  • (condition ? valueIfTrue : valueIfFalse)