Document Object Model

  • DOM: It is a tree of nodes or elements created by the browser.
  • It is a structured representation of an HTML document.
  • Java Script is used to read/write/manipulate the DOM.
console.log(document);

Window Object

It is the GLOBAL OBJECT in client-side java script

window.console.log("hey, there!");

=

console.log("hey, there!");

Document  is a part of Window Object.

It includes methods like console(),  prompt(), alert(), confirm() etc,.

if window.confirm(" Do you confirm to delete the file?")
{    window.console.log("file deleted"); 
}
 else
{
    window.console.log("Prevented deleting the file");
}

Document Object

// gives an array of all the element nodes present in the HTML document
document.all;

// gives the number of element nodes in the HTML document
document.all.length;

// gives the <head> tag of the HTML document
document.head;

// gives you the <body> tag of the HTML document
document.body;

// gives you the DOCTYPE of the HTML document
document.doctype;

// gives you the URL of the website
document.URL;

// gives you a list of all the images in the HTML document
document.images;

Like every other object in Object-oriented programming language, document object has a few properties.

DOM selectors

  • Single Element selectors
  • Multiple Element selectors

Single Element selectors

  • document.getElementByID()
  • document.querySelector()

document.getElementById()

menu = document.getElementById('menu');
console.log("\n GET ELEMENT BY ID\n",menu, typeof menu);

console.log(menu.className);  // returns the className
console.log(menu.id);         // returns the Id

// we can even style the elements using DOM
menu.style.backgroundColor = "#FFADA3";

document.querySelector()

listItems = document.querySelector('.list-items');
console.log("\n QUERY SELECTOR\n",listItems, typeof listItems);

menu_q = document.querySelector('#menu');
list = document.querySelector('.list');
li = document.querySelector('li');
console.log(menu_q, list, li);

// >>>>>>>>>>>>> you can even select a particular element using pseudo classes
//  in CSS , nested elements <<<<<<<<<<<<<
list.querySelector('.item:last-child').style.border = "solid 3px #FC34CF";

document.querySelector('.card:last-child').innerHTML = "<p> this is done using query selector where a last div is selected using pseudo classes</p><p> And this seems to replace all the inner child elements of the last .card div to two p tags with text";

Multiple Element Selectors

  • document.getElementsByClassName()

  • document.getElementsByTagName()
  • document.querySelectorAll()

document.getElementsByClassName()

listItems = document.getElementsByClassName("list-items");
console.log(`\n GET ELEMENTS BY CLASS NAME\n ${listItems}`, listItems);

listItems[3].style.color = "#AD45E1";

// local scoping of selecting an element
listItems[2].getElementsByTagName("div")[1].style.backgroundColor = "#7FF2F3"; 

console.log(menu.id);         // returns the Id

// we can even style the elements using DOM
menu.style.backgroundColor = "#FFADA3";

listItems = Array.from(listItems);
console.log(listItems);
listItems.forEach(function(li, i) {
  console.log(li);
});

document.querySelectorAll()

card = document.querySelectorAll(".card");
console.log(`\n QUERY SELECTOR ALL\n ${card}`);
console.log(card);
contactCard = document.querySelectorAll(".contact-card");
console.log(contactCard);

for (let i = 0; i < contactCard.length; i++) {
  contactCard[i].style.border = "dashed 3px #FFFFFF";
}

divItems = document.getElementsByTagName("div");
console.log(`\n GET ELEMENTS BY TAG NAME\n ${divItems}`);

document.getElementsByTagName()

Traversing the DOM

Moving up and down and dealing with the parents and children of the specific nodes we select is known as DOM traversing

  • child Node and children
  • children of children
  • parent
  • parent of parent

child node

Gives you a Node List of all the child nodes of the selected element, including the text nodes.

const list = document.querySelector('.list-ul');

let val = list.childNodes;

val = list.childNode[2];

children

Gives you an HTML Collection of only the element nodes of the selected element.

let val = list.children;

val = list.children[3];

val.style.background = "#00DE67";

children of children

const list = document.querySelector('.list-ul');

let val = list.children;

val = list.children[2].children;

parent Element

let val = list.parent;

val = list.parentNode;

parent of parent

let val = list.parentElement.parentElement;

Creating DOM elements

  1.  get the element you want to append the created element
  2. create an element
  3. append the created element to (1)
  •  get the element  - document.querySelector(' ');
  • create an element - document.createElement('tagName');
  • append the created element - prevElement.appendChild(newElement);
// get the element
const card = document.querySelector(".card");

// create a new DOM element
const div = document.createElement('div');

// append the new created element to the card
card.appendChild(div);

Replacing the DOM elements

  1. create an element
  2. get the previous element
  3. get the parent of the previous element
  4. replace the element
  • create an element - document.createElement('tagName')
  • get the previous element - document.getElementById('id')
  • get the parent of the previous element - prevElement.parentElement;
  • replace the element - parent. replaceChild('newElement', 'oldElement')
// creating a new element
const newPara = document.createElement('p');

// getting the previous element
const oldPara = document.getElementById('About');

// getting the parent of the previous element
const parent = oldPara.parentElement;

// replacing newPara with oldPara
parent.replaceChild(newPara, oldPara);

Removing DOM elements

  1. get the element
  2. remove the element
// getting the element
const li = document.querySelectorAll('li');

// getting the parent element 
const ul = document.querySelector('ul');

// remove the element
li[3].remove();

// remove the child element
ul.removeChild(li[4]);
  • get the element - document.getElementById();
  • remove the element :
    • remove the selected element - element.remove();
    • remove the child element of the selected element - element.removeChild(child[2])

Note: u need to get the child element using DOM selectors before removing it.

TASK

Document-Object-Model

By Supriya kotturu

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Document-Object-Model

javaScript - DOM

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