**INTRODUCTION TO DOM** When a web page is loaded, the browser creates a Document object model(DOM) of the page. which is the tree representation of an HTML document and the DOM tree is modified with JavaScript. ```html

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``` ![Alt Text](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/bi2gqoddvbhg71c9qvlm.png) **JavaScript And DOM** 1. JavaScript can add new HTML elements and attributes. 2. JavaScript can change all the CSS styles in a page 3. JavaScript can add and listen to HTML events like onScroll hover onclick, etc. 4. JavaScript can change any HTML elements and attributes of a page. 5. JavaScript can remove existing HTML elements and attributes. Now, how do we add JavaScript to an HTML documents ```html ``` checking your console, would prompt that it is active. **SELECTING HTML DOCUMENTS** This is when selecting HTML with JavaScript, and it provides a DOM method ```js getElementById('targeted-html-doc'); ``` getElementById is a DOM method which accepts the HTML elements ID,and returns the HTML elements matching that Id. example: ```js document.getElementById('#navBar'); ``` You need to pass the ID of the elements as an arguments, if no element matches the Id then it returns null. **Query Selector** Query selector allows you to use CSS selector to select HTML elements. It is the new way in JavaScript to select elements. There are two types of query selector; ```js querySelector(); querySelectorAll(); ``` query selector is a DOM method. It's accepts the CSS selectors string and only returns the first HTML elements, matching the query, example; ```js document.querySelector('#footer span'); ``` You need to pass the CSS. Selector strings as an argument,If no elements matches the Selector string, then it returns null. while querySelectorall is a DOM method that accepts the CSS selector string, and return all of the HTML elements, matching the query. example; ```js document.querySelectorAll('#footer span'); ``` we need to pass the CSS selector string as an argument, If no element that matches, then it returns an empty array

beginnersjs

DOCUMENT OBJECT MODEL(DOM)

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