JavaScript console.log()

The JavaScript console.log() function is one of the most useful tools for developers. It allows you to print messages or data to the browser’s console, which is helpful for debugging, understanding how your code is working, and displaying temporary output.

Common uses of console.log include:

  • Debugging: Display the values of variables during program execution.
  • Output tracking: See the flow of your program and the state of data.
  • Learning: Practice and understand how code behaves.

What You'll Learn

You’ll learn how to use the console.log function to output text, numbers, and variables in JavaScript. This is the first step in understanding how to interact with JavaScript programs in the browser environment.

Understanding the console.log Function

The basic syntax is simple:

javascript
console.log(message);
  • message: This can be a string, number, variable, object, or any other value you want to display.

When you run your JavaScript code in Node.js, the output from console.log will appear directly in your terminal or command line.

To try it out, create a file like example.js and run it using the command:

node example.js

Example 1: Printing a Simple Message

To print a simple message in JavaScript, pass the message inside the console.log function with quotation marks. This will output the message to the terminal if you're using Node.js.

javascript
console.log("Welcome to JavaScript");

How It Works:

  • console.log: This is the JavaScript function used to print output to the terminal or console.
  • "Welcome to JavaScript Tutorial": This is a string — a piece of text enclosed in quotation marks.
  • When the code is run in a Node.js environment, JavaScript sends the string "Welcome to JavaScript Tutorial" to the console using the console.log function. The result is that the message appears in the terminal.

Output

Welcome to JavaScript

Example 2: Logging Numbers

You can log numbers directly in JavaScript using console.log. This is helpful when you want to inspect numeric values or the result of a calculation.

javascript
console.log(42);

How It Works:

  • console.log: This function is used to print output to the console.
  • 42: This is a number (integer). JavaScript recognizes it as a numeric literal and outputs it directly.
  • When the code is run in a Node.js environment, it will print the number 42 to the console.

Output

42

Example 3: Logging Multiple Values

You can log multiple values in a single console.log call. JavaScript separates the values with a space in the console output.

javascript
console.log("You have", 5, "messages.");

How It Works:

  • console.log: The JavaScript function used to print output to the console.
  • "You have": A string containing the message that will be printed.
  • 5: A number, which will be displayed next to the string.
  • "messages.": Another string, which follows the number.
  • When the code runs, "You have 5 messages." is printed in the console. Notice how the string and number are separated by spaces.

Output (in console)

You have 5 messages.

Exercises

Try these beginner-friendly tasks to get hands-on with console.log.

1. Print your name to the console.
javascript
// Exercise 1: Print your name
console.log("Your Name");
2. Print your favorite programming language.
javascript
// Exercise 2: Print your favorite language
console.log("JavaScript");
3. Print your age.
javascript
// Exercise 3: Print your age
let age = 25;
console.log(age);

*Tip: Use console.log() frequently to see what your code is doing as you learn!

Frequently Asked Questions

What does the console.log() function do in JavaScript?

The console.log() function in JavaScript outputs the specified message or value to the console. It's commonly used for debugging, logging, and displaying results.

Can I log multiple values at once using console.log()?

Yes, you can log multiple values by separating them with commas inside the console.log() function. JavaScript will display them in the console.

Do I need quotation marks for everything I log in JavaScript?

Only strings (text) need to be inside quotation marks. Numbers and variables can be logged directly without quotes.

Why is my console output not visible in the browser?

If your console output is not visible, make sure you have the browser's developer tools open and the 'Console' tab selected. If you're using certain browsers, check the settings to ensure console logs are enabled.

Can console.log() be used for debugging JavaScript code?

Absolutely! console.log() is one of the most widely used methods for debugging. You can log variables, objects, and values at different points in your code to check for errors and monitor program flow.

What's Next?

Next, you'll learn about variables in JavaScript. Variables let you store and reuse values in your code, which is essential for doing anything useful in programming.