JavaScript Output

innerHTML, console.log, alert and more.

✍️ 3 exercises + code challenge in this lesson

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JavaScript can display data in several ways:

element.innerHTML / textContent: write into an HTML element.
console.log(): write to the browser console (press F12 to see it). Best for debugging.
window.alert(): show a popup box.
document.write(): writes directly into the page (only for testing).

The examples in this tutorial use a small log() helper that prints into the result pane, so you can see output without opening the console.

Key Takeaways: JavaScript Output

Mastering JavaScript Output helps you write clean and reliable JavaScript code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

JavaScript Output Code Example

JavaScript

<pre id="out"></pre>
<script>
const log = (...a) => document.getElementById("out").textContent += a.join(" ") + "\n";
log("Hello from log()");
console.log("This one goes to the browser console (F12)");
document.body.insertAdjacentHTML("beforeend", "<h3>Written with insertAdjacentHTML</h3>");
</script>
<button onclick="alert('An alert box!')">Show alert</button>

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JavaScript Output Practice Exercises

Check what you learned in “JavaScript Output”.

/ 3 solved

Fill in the blank

Write a message to the browser console.

.log("Debugging...");

✓ Correct! Not quite. Try again.

Multiple choice

Which method shows a popup message box?

alert() popup() message() console.box()

✓ Correct! Not quite. Try again.

Code challenge

Use log() to print the text Hello, Output!

Write the code in the live editor. Your answer is checked automatically.

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to save your exercise progress.

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JavaScript Statements

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JavaScript Output

💡 Key Takeaways: JavaScript Output

JavaScript Output Code Example

JavaScript Output Practice Exercises

Key Takeaways: JavaScript Output