Category: JavaScript

JavaScript Reserved Words

In JavaScript you cannot use these reserved words as variables, labels, or function names:

abstract arguments await* boolean
break byte case catch
char class* const* continue
debugger default delete do
double else enum* eval
export* extends* false final
finally float for function
goto if implements import*
in instanceof int interface
let* long native new
null package private protected
public return short static
super* switch synchronized this
throw throws transient true
try typeof var void
volatile while with yield

Words marked with* was new in ECMAScript 5 and ECMAScript 6.

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JavaScript Output

JavaScript Display Possibilities

JavaScript can “display” data in different ways:

  • Writing into an HTML element, using innerHTML.
  • 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 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>

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JavaScript Where To

The <script> Tag

In HTML, JavaScript code is inserted between <script> and </script> tags.

Example

<script>
document.getElementById("demo").innerHTML = "My First JavaScript";
</script>

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JavaScript Introduction

What is JavaScript?

JavaScript is the programming language of the web.

It can update and change both HTML and CSS.

It can calculate, manipulate and validate data.

Why Study JavaScript?

JavaScript is one of the 3 languages all web developers must learn :

1. HTML to define the content of web pages

2. CSS to specify the layout of web pages

3. JavaScript to program the behavior of web pages

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