JavaScript Output

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JavaScript does NOT have any built-in print or display functions.

JavaScript Display Possibilities

JavaScript can "display" data in different ways:

window.alert() : 경고창
document.write() : HTML출력
innerHTML : HTML요소 작성(태그 내부값을 읽고, 설정)
console.log() : 콘솔로그 쓰기

Using window.alert()

You can use an alert box to display data:

Example

<!DOCTYPE html>
<html>
<body>

<h1>My First Web Page</h1>
<p>My first paragraph.</p>

<script>
window.alert(5 + 6);
</script>

</body>
</html>

Try it Yourself »

Using document.write()

For testing purposes, it is convenient to use document.write():

Example

<!DOCTYPE html>
<html>
<body>

<h1>My First Web Page</h1>
<p>My first paragraph.</p>

<script>
document.write(5 + 6);
</script>

</body>
</html>

Try it Yourself »

Using document.write() after an HTML document is fully loaded, will delete all existing HTML:

Example

<!DOCTYPE html>
<html>
<body>

<h1>My First Web Page</h1>
<p>My first paragraph.</p>

<button onclick="document.write(5 + 6)">Try it</button>

</body>
</html>

Try it Yourself »

	The document.write() method should be used only for testing.

Using innerHTML

To access an HTML element, JavaScript can use the document.getElementById(id) method.

The id attribute defines the HTML element. The innerHTML property defines the HTML content:

Example

<!DOCTYPE html>
<html>
<body>

<h1>My First Web Page</h1>
<p>My First Paragraph</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML = 5 + 6;
</script>

</body>
</html>

Try it Yourself »

	To "display data" in HTML, (in most cases) you will set the value of an innerHTML property.

Using console.log()

In your browser, you can use the console.log() method to display data.

Activate the browser console with F12, and select "Console" in the menu.

Example

<!DOCTYPE html>
<html>
<body>

<h1>My First Web Page</h1>
<p>My first paragraph.</p>

<script>
console.log(5 + 6);
</script>

</body>
</html>

Try it Yourself »

저작자표시 비영리 (새창열림)