DOM (Document Object Model) is an in-memory representation of HTML documents. It represents the webpage as a JS object so that JS programs can modify it.
These are some of the APIs for DOM manipulation:
HTML DOM methods are actions you can perform (on HTML Elements).
HTML DOM properties are values (of HTML Elements) that you can set or change.
In the DOM, all HTML elements are defined as objects.
The programming interface is the properties and methods of each object.
A property is a value that you can get or set (like changing the content of an HTML element).
A method is an action you can do (like add or deleting an HTML element).
Example
Add an event listener that fires when a user clicks a button:
document.getElementById("myBtn").addEventListener("click", displayDate);
Stuff I Have Learnt 