# JavaScript Your First Program: console.log Basics for Beginners Source: https://devdocs10.com/articles/javascript/js-first-program By Murat Bo · Published 2026-06-25 · DevDocs10 (https://devdocs10.com) Your first JavaScript program is usually a simple `console.log()` call. It prints text or values so you can confirm that JavaScript is running and start learning how code produces output. > **Quick answer:** Use `console.log()` to send output to the browser console or terminal. For example, `console.log('Hello, world!')` prints a message and is the standard first step in JavaScript. > **Difficulty:** Beginner > > **You'll understand this better if you know:** how to open a code editor, what a string is, and the basic idea that JavaScript runs statements one line at a time. ## 1. What Is console.log()? `console.log()` is a built-in JavaScript method that writes a message to the console. The console is a developer tool in the browser or a text output area in Node.js. - It is used to display text, numbers, variables, and objects. - It helps you test code without building a user interface. - It is one of the simplest ways to see what your program is doing. - It does not show anything on the web page by itself. For beginners, this is often the first complete program because it proves that your JavaScript file is working. ## 2. Why console.log() Matters Printing output is one of the fastest ways to learn programming. With `console.log()`, you can check whether your code runs, inspect values, and understand how statements behave. It matters because JavaScript often runs in places where you cannot see internal values directly. Logging gives you a simple feedback loop while you learn syntax, variables, functions, and control flow. ## 3. Basic Syntax ### The simplest form The basic pattern is a call to the `console` object’s `log` method, followed by parentheses containing the value you want to print. ```javascript console.log('Hello, world!'); ``` Output (tested with Node 24.21.0): ```text Hello, world! ``` This example prints the text `Hello, world!` to the console. The quotation marks make it a string. ### What each part means - `console` is the built-in object that handles developer output. - `log` is the method you call on that object. - `()` contains the value or values to display. - `;` ends the statement in a clear, conventional way. ## 4. Step-by-Step Examples ### Example 1: Print a simple message This is the classic first program. It confirms that JavaScript can run and produce output. ```javascript console.log('Hello, world!'); ``` Output (tested with Node 24.21.0): ```text Hello, world! ``` When you run this code, the console shows the message exactly as written inside the quotes. ### Example 2: Print a number You do not need quotes for numbers. JavaScript prints the numeric value directly. ```javascript console.log(42); ``` Output (tested with Node 24.21.0): ```text 42 ``` This is useful when you want to confirm calculations or check hard-coded values. ### Example 3: Print a variable Logging a variable is one of the most common uses of `console.log()`. It helps you see what value the variable currently holds. ```javascript const name = 'Ava'; console.log(name); ``` Output (tested with Node 24.21.0): ```text Ava ``` The console shows `Ava`, not the word `name`, because the variable is evaluated before printing. ### Example 4: Print multiple values You can pass more than one value to `console.log()`. JavaScript prints them separated by spaces in the console. ```javascript const language = 'JavaScript'; const year = 2026; console.log(language, year); ``` Output (tested with Node 24.21.0): ```text JavaScript 2026 ``` This is helpful for checking related values together during debugging. ### Example 5: Print a formatted sentence You can also combine text and variables into one message with a template literal. ```javascript const user = 'Mina'; const score = 18; console.log(`User ${user} scored ${score} points`); ``` Output (tested with Node 24.21.0): ```text User Mina scored 18 points ``` This is a natural way to build readable output without string concatenation. ## 5. Practical Use Cases - Checking that a script file is connected and running. - Verifying that a browser or Node.js environment is executing your code. - Inspecting variable values while learning or debugging. - Tracing the order in which functions run. - Confirming the result of a calculation before using it elsewhere. In real projects, developers often use `console.log()` as a temporary debugging tool, then remove or replace it later with proper UI output or structured logging. ## 6. Common Mistakes ### Mistake 1: Forgetting the parentheses `console.log` is a function call. If you leave off the parentheses, JavaScript refers to the function itself instead of running it. **Problem:** This does not print anything because the method is never called. ```javascript console.log; ``` **Fix:** Add parentheses and pass the value you want to print. ```javascript console.log('Hello!'); ``` Output (tested with Node 24.21.0): ```text Hello! ``` The corrected version works because the function is actually executed. ### Mistake 2: Using an undefined variable Beginners often try to print a value before creating it. In that case, JavaScript cannot find the variable and throws a reference error. **Problem:** The name has not been declared, so the console reports an error like `ReferenceError: message is not defined`. ```javascript console.log(message); ``` Output (tested with Node 24.21.0): ```text Uncaught ReferenceError: message is not defined ``` **Fix:** Declare the variable before logging it. ```javascript const message = 'Ready to go'; console.log(message); ``` Output (tested with Node 24.21.0): ```text Ready to go ``` The fixed version works because the variable exists when `console.log()` runs. ### Mistake 3: Expecting output on the web page `console.log()` writes to the console, not to the HTML document. This is one of the most common early misunderstandings. **Problem:** The code runs, but nothing appears in the page content because console output is separate from page rendering. ```javascript console.log('Visible in the console only'); ``` Output (tested with Node 24.21.0): ```text Visible in the console only ``` **Fix:** If you want visible page content, write to the DOM instead of the console. ```javascript const output = 'Visible on the page'; document.querySelector('#app').textContent = output; ``` The corrected version works because it updates page content instead of logging to the console. ## 7. Best Practices ### Use clear, descriptive messages When logging text, make it easy to understand later. A vague message like `done` is less useful than a specific one. ```javascript console.log('User profile loaded'); ``` Output (tested with Node 24.21.0): ```text User profile loaded ``` This kind of message helps you read logs quickly, especially when several statements run in sequence. ### Log the value you need, not everything It is tempting to print entire objects or many variables at once, but focused logs are easier to scan. ```javascript const total = 99; console.log('Total price:', total); ``` Output (tested with Node 24.21.0): ```text Total price: 99 ``` Small, targeted logs make debugging faster and reduce noise in the console. ### Remove temporary logs when they are no longer needed Logging is great during development, but too many leftover logs make real debugging harder. ```javascript // Temporary while testing console.log('Checking step 1'); ``` Output (tested with Node 24.21.0): ```text Checking step 1 ``` Once the code is stable, delete or replace temporary logging so the output stays meaningful. ## 8. Limitations and Edge Cases - `console.log()` does not show anything to normal users unless they open developer tools or inspect terminal output. - Browser consoles and Node.js terminals may format objects differently. - Some environments hide logs in production builds or filter them automatically. - Logging does not pause code execution; it only reports values. - Very large objects can be hard to read because consoles often show them in an expandable format. If `console.log()` appears to be "not working," the most common causes are that the console is closed, the script never loaded, or the code has an earlier syntax error that stops execution. ## 9. Practical Mini Project This tiny program greets a user and confirms a calculation. It shows how `console.log()` fits into a real script, not just a one-line example. ```javascript const firstName = 'Riya'; const items = 3; const pricePerItem = 12; const totalPrice = items * pricePerItem; console.log(`Hello, ${firstName}!`); console.log('Items:', items); console.log('Total price:', totalPrice); ``` Output (tested with Node 24.21.0): ```text Hello, Riya! Items: 3 Total price: 36 ``` Expected output: ```javascript Hello, Riya! Items: 3 Total price: 36 ``` This example combines strings, variables, and arithmetic so you can see how a small program produces readable output. ## 10. Key Points - `console.log()` prints output for debugging and learning. - It works in browsers and in Node.js, but the output destination is different. - You must call it with parentheses to run it. - It does not display anything on the page by itself. - It is a development tool, not usually the final way users see results. ## 11. Practice Exercise Write a small JavaScript program that prints three lines to the console: your name, your favorite language, and a simple calculation result. - Use one `console.log()` call for each line. - Include at least one variable. - Make the third line show a calculation such as `2 + 3` or `5 * 4`. Expected output: ```javascript Your Name Favorite language: JavaScript Calculation result: 20 ``` Hint: Store the name and language in variables first, then log them with a sentence. Solution: ```javascript const myName = 'Sam'; const favoriteLanguage = 'JavaScript'; const calculationResult = 5 * 4; console.log(myName); console.log(`Favorite language: ${favoriteLanguage}`); console.log(`Calculation result: ${calculationResult}`); ``` Output (tested with Node 24.21.0): ```text Sam Favorite language: JavaScript Calculation result: 20 ``` ## 12. Final Summary Your first JavaScript program is usually a simple `console.log()` statement, but it teaches an important habit: run code, inspect output, and verify that your assumptions are correct. That makes it one of the most useful beginner tools in JavaScript. As you continue learning, you will use `console.log()` to test variables, trace logic, and spot mistakes before they become bigger problems. The next natural step is to learn variables and expressions so you can print values that your program calculates dynamically.