<script></script>

The script element allows develop to add JavaScript code inside an HTML file.

The defer attribute specifies scripts should be executed after the HTML file is completely parsed. When the HTML parser encounters a <script> element with the defer attribute, it loads the script but defers the actual execution of the JavaScript until it finishes parsing the rest of the elements in the HTML file.

The async attribute loads and executes the script asynchronously with the rest of the webpage. This means that, similar to the defer attribute, the HTML parser will continue parsing the rest of the HTML as the script is downloaded in the background. However, with the async attribute, the script will not wait until the entire page is parsed: it will execute immediately after it has been downloaded

console.log('Codecademy'.toUpperCase());
console.log('    Remove whitespace   '.trim());
console.log(Math.random());
Math.floor(Math.random() * 50);

console.log(Math.floor(Math.random() * 100));
console.log(Math.ceil(43.8));
console.log(Number.isInteger(2017));

console.log('Hello'.toLowerCase())

• Data is printed, or logged, to the console, a panel that displays messages, with console.log().
• We can write single-line comments with // and multi-line comments between /* and /.
• There are 7 fundamental data types in JavaScript: strings, numbers, booleans, null, undefined, symbol, and object.
• Numbers are any number without quotes: 23.8879
• Strings are characters wrapped in single or double quotes: 'Sample String'
• The built-in arithmetic operators include +, , , /, and %.
• Objects, including instances of data types, can have properties, stored information. The properties are denoted with a . after the name of the object, for example: 'Hello'.length.
• Objects, including instances of data types, can have methods which perform actions. Methods are called by appending the object or instance with a period, the method name, and parentheses. For example: 'hello'.toUpperCase().
• We can access properties and methods by using the ., dot operator.
• Built-in objects, including Math, are collections of methods and properties that JavaScript provides.