JavaScript Output
JavaScript can
"display" data in different ways:
Writing into an HTML
element, using inner HTML.
Writing into the HTML output
using document. Write ().
Writing into an alert box,
using window .alert().
Writing into the browser
console, using console.log().
Using inner HTML
To access an HTML element,
JavaScript can use the document .get Element By Id (id) method.
The id attribute defines the
HTML element. The inner HTML 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>
»
Changing the innerHTML
property of an HTML element is a common way to display data in HTML.
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>
»
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>
»
The document.write() method
should only be used for testing.
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>
»
Using console.log()
For debugging purposes, you
can use the console.log() method to display data.
You will learn more about
debugging in a later chapter.
Example
<!DOCTYPE html>
<html>
<body>
<script>
console.log(5 + 6);
</script>
</body>
</html>
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