Functions - Built in

Function allows us to group together multiple statements, take in some values, perform some operations and return some value.

Functions take in data known as arguments.

Function may or may not return a value.

Example:

Math.max(10, 12); // 12

The above line is a JavaScript statement.

10 and 12 passed to the function are arguments, separated by comma.

12 is returned from the function.

There are many in-built JavaScript functions.

e.g:

console.log('hey'); returns undefined , logs hey.
parseFloat('2.032565') // 2.032565 (converts string to number)
parseInt('2.032565') // 2 (converts string to number as integer)
Many date functions are also present. e.g. Date.now() returns no. of milliseconds since January 1, 1970 00:00:00 UTC.
DOM functions:

Example:

<body>
<p>Hey How ya doin?</p>
	<script>
		const para = document.querySelector('p'); // finds p tag in page
		console.log(para); // <p>Hey How ya doin?</p>
	</script>
</body>

Mobile only functions e.g. navigator.vibrate()

In case of doubts, always refer MDN Docs.

Other Examples:

scrollTo(0, 200); // scrolls to (x, y) position in page

scrollTo({
	top: 500,
	left: 0,
	behavior: 'smooth'
}); // scrolls to position top: 500, left: 0 in a 'smooth' manner

The scrollTo function returns undefined.