Question

What is the output?

function sayHi(name) {
  return `Hi there, ${name}`;
}

console.log(sayHi());

• A: Hi there,
• B: Hi there, undefined
• C: Hi there, null
• D: ReferenceError

Answer 1

Answer: B

By default, arguments have the value of undefined, unless a value has been passed to the function. In this case, we didn't pass a value for the name argument. name is equal to undefined which gets logged.

In ES6, we can overwrite this default undefined value with default parameters. For example:

function sayHi(name = "Lydia") { ... }

In this case, if we didn't pass a value or if we passed undefined, name would always be equal to the string Lydia