JavaScript Function Parameters Lab

Learning Goals

Define a function that uses a parameter
Define a function that uses two parameters
Define a function with a parameter that has a default value

Introduction

In this lab, we'll practice using parameters in our functions. We'll also learn how to create a default value for a parameter.

If you haven't already, fork and clone this lab into your local environment. Navigate into its directory in the terminal, then run code . to open the files in Visual Studio Code. (If you are using a different text editor, the command will be different.)

You will be writing your code in the index.js file and running the tests by running learn test in the terminal.

Define a Function That Uses a Parameter

Instructions: Define a function called introduction that defines a parameter, name, and returns the phrase: "Hi, my name is ${name}."

Define a Function That Uses Two Parameters

Setting up your function to use two parameters is straightforward: simply include both parameters in the parentheses in the function declaration line, separated by a comma:

function logTwoValues(value1, value2) {
  console.log(`The two values are ${value1} and ${value2}.`);
}

As you might expect, if we instead wanted to log three values — or ten values — we can just continue listing the parameters in the parentheses, with commas between each.

Instructions: To pass the second test, you'll need to define a function called introductionWithLanguage that defines two parameters, name and language, and returns the phrase: "Hi, my name is [name] and I am learning to program in [language]."

Define a Function That Uses an Optional Parameter

In a previous lesson, we created a function that logs a personalized greeting:

function sayHelloTo(firstName) {
  console.log(`Hello, ${firstName}!`);
}

What if we wanted to make this function work whether or not a first name is passed in as an argument? We can do this by setting a default value for the firstName parameter:

function sayHelloTo(firstName = "User") {
  console.log(`Hello, ${firstName}!`);
}

Note that we have used the assignment operator (=) here to assign a default value. The way this works is, if the function is called with an argument, the argument's value will supersede the default value. If it's called without an argument, the function will use the default value, logging "Hello, User!"