HTML document is structured as a JavaScript Object. Every HTML element has a different properties which can help to manipulate it. It is possible to get, create, append or remove HTML elements using JavaScript. Check the examples below. Selecting HTML element using JavaScript is similar to selecting using CSS. To select an HTML element, we use tag name, id, class name or other attributes.
### Getting Element
We can access already created element or elements using JavaScript. To access or get elements we use different methods. The code below has four _h1_ elements. Let us see the different methods to access the _h1_ elements.
**_getElementsByTagName()_**:takes a tag name as a string parameter and this method returns an HTMLCollection object. An HTMLCollection is an array like object of HTML elements. The length property provides the size of the collection. Whenever we use this method we access the individual elements using index or after loop through each individual items. An HTMLCollection does not support all array methods therefore we should use regular for loop instead of forEach.
console.log(allTitles[i]) // prints each elements in the HTMLCollection
}
```
#### Getting elements by class name
**_getElementsByClassName()_** method returns an HTMLCollection object. An HTMLCollection is an array like list of HTML elements. The length property provides the size of the collection. It is possible to loop through all the HTMLCollection elements. See the example below
let firstTitle = document.querySelector('#first-title') // select id with first-title
let firstTitle = document.querySelector('.title') // select the first available h2 element with class title
```
**_querySelectorAll_**: can be used to select html element by its tag name or class. It return a nodeList which is an array like object which support array methods. We can use **_for loop_** or **_forEach_** to loop through each nodeList elements.
const allTitles = document.querySelectorAll('.title') // the same goes for selecting using class
```
### Adding attribute
An attribute is added in the opening tag of HTML which gives additional information about the element. Common HTML attributes: id, class, src, style, href,disabled, title, alt. Lets add id and class for the fourth title.
```js
const titles = document.querySelectorAll('h1')
titles[3].class = 'title'
titles[3].id = 'fourth-title'
```
#### Adding attribute using setAttribute
The **_setAttribute()_** method set any html attribute. It takes two parameters the type of the attribute and the name of the attribute.
Let's add class and id attribute for the fourth title.
```js
const titles = document.querySelectorAll('h1')
titles[3].setAttribute('class', 'title')
titles[3].setAttribute('id', 'fourth-title')
```
#### Adding attribute without setAttribute
We can use normal object setting method to set an attribute but this can not work for all elements. Some attributes are DOM object property and they can be set directly. For instance id and class
```js
//another way to setting an attribute
titles[3].className = 'title'
titles[3].id = 'fourth-title'
```
#### Adding class using classList
The class list method is a good method to append additional class. It does not override the original class if a class exists rather it adds additional class for the element.
```js
//another way to setting an attribute: append the class, doesn't over ride
titles[3].classList.add('title', 'header-title')
```
#### Removing class using remove
Similar to adding we can also remove class from an element. We can remove a specific class from an element.
```js
//another way to setting an attribute: append the class, doesn't over ride
An HTML is a build block of an opening tag, a closing tag and a text content. We can add a text content using the property _textContent_ or \*innerHTML.
#### Adding Text content using textContent
The _textContent_ property is used to add text to an HTML element.
Most people get confused between _textContent_ and _innerHTML_. _textContent_ is meant to add text to an HTML element, however innerHTML can add a text or HTML element or elements as a child.
The innerHTML property can allow us also to remove all the children of a parent element. Instead of using removeChild() I would recommend the following method.
As you have notice, the properties of css when we use it in JavaScript is going to be a camelCase. The following CSS properties change from background-color to backgroundColor, font-size to fontSize, font-family to fontFamily, margin-bottom to marginBottom.
🌕 Now, you are fully charged with a super power, you have completed the most important and challenging part of the challenge and in general JavaScript. You learned DOM and now you have the capability to build and develop applications. Now do some exercises for your brain and for your muscle.
1. Change stye of each paragraph using JavaScript(eg. color, background, border, font-size, font-family)
1. Select all paragraphs and loop through each elements and give the first and third paragraph a color of green, and the second and the fourth paragraph a red color
1. Set text content, id and class to each paragraph
1. Develop the following application, use the following HTML elements to get started with. You will get the same code on starter folder. Apply all the styles and functionality using JavaScript only.
