Document object model(DOM)

what is DOM?

The Document Object Model (DOM) is a programming interface for web documents. It represents the page so that programs can change the document structure, style, and content. The DOM represents the document as nodes and objects; that way, programming languages can interact with the page.

A web page is a document that can be either displayed in the browser window or as the HTML source. In both cases, it is the same document but the Document Object Model (DOM) representation allows it to be manipulated. As an object-oriented representation of the web page, it can be modified with a scripting language such as JavaScript.

The HTML DOM Tree of Objects

DOM HTML tree

With the object model, JavaScript gets all the power it needs to create dynamic HTML:

  • JavaScript can change all the HTML elements in the page
  • JavaScript can change all the HTML attributes in the page
  • JavaScript can change all the CSS styles in the page
  • JavaScript can remove existing HTML elements and attributes
  • JavaScript can add new HTML elements and attributes
  • JavaScript can react to all existing HTML events in the page
  • JavaScript can create new HTML events in the page

The DOM Programming Interface

The HTML DOM can be accessed with JavaScript (and with other programming languages).

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

The following example changes the content (the innerHTML) of the <p> element with id="demo":

Example

<html>
<body>

<p id=”demo”></p>

<script>
document.getElementById(“demo”).innerHTML = “Hello World!”;
</script>

</body>
</html>

In the example above, getElementById is a method, while innerHTML is a property.

The getElementById Method

The most common way to access an HTML element is to use the id of the element.

In the example above the getElementById method used id="demo" to find the element.

The innerHTML Property

The easiest way to get the content of an element is by using the innerHTML property.

The innerHTML property is useful for getting or replacing the content of HTML elements.

The innerHTML property can be used to get or change any HTML element, including <html> and <body>.

References:

https://www.w3schools.com/js/js_htmldom_methods.asp

https://developer.mozilla.org/en-US/docs/Web/API /Document_Object_Model/Introduction

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