Guide: Document Object Model (DOM): Complete Guide
We’ve all heard of the DOM, or Document Object Model, which is mentioned from time to time, related to JavaScript. DOM is a pretty important concept in web development. We couldn’t do without it Dynamically change HTML pages in the browser. Learning and understanding the DOM results in better ways of open, change and monitor various elements of an HTML page. The Document Object Model can also help us reduce unnecessary increases in script execution time
Data structure trees
Before we talk about what the DOM is, how it arises, how it exists, and what happens inside, I want you to know a little bit about trees. Not the coniferous and deciduous kind, but about the data structure boom The concept of data structures is a lot easier to understand if we simplify their definition. I would say a data structure is about organizing your dataYes, just an old arrangement, such as you would arrange the furniture in your home or the books in a bookshelf or put all the different food groups you eat on your plate for a meal make it meaningful to you That is of course not all there is in a data structure, but that is where it all starts. This “arrangement” is at the heart everything. It’s also pretty important in the DOM. But we’re not talking about DOM yet, so let me take you to one data structure you may be familiar with: arrays Have arrays indices and length, they can be multidimensional, and have many more features. As important as it is to know these things about arrays, let’s not get into that now. For us, an array is quite simple. It’s when you put different things in a row Likewise, when we think of trees, let’s say it’s about going putting things together, starting with just one thing at the top.
Now maybe you can take the ducks from the past put it upright, and tell me that “now every duck is under another duck”. Is it then one boom? It is. Depending on what your data is or how you plan to use it, the top data in your family tree (the carrotmaybe something that is very important or something that is alone enclose other elements underneath Either way, the topmost element in a data structure in a boom is doing something very important. It offers a place start by looking for all the information we get from the boom want to get
The meaning of DOM
DOM stands for Document Object ModelThe document refers to an HTML (XML) document that is displayed as an object(In JavaScript, everything can always be displayed only as an object!) The model is created by the browser that takes an HTML document and creates an object that represents it. We can access this object with JavaScript. And since we use this object to manipulate the HTML document and build our own applications, DOM is basically an API
The DOM structure
In JavaScript code, it is HTML document displayed as an objectAll data read from that document is also saved as objects, nested one below the other (because as I said before, in JavaScript, everything can always only be displayed as objects). So this is basically the physical arrangement of DOM data in code: everything is arranged as objectsBut logically it is a boom
The DOM parser
Every browser software has a program called DOM parser that is responsible for parsing an HTML document in DOM Browsers read an HTML page and convert the data into objects that make up the Dom. The information contained in these JavaScript DOM objects is logically arranged as a data structure tree known as the DOMboom.
Parse data from HTML to DOM structure
Take a simple HTML file. It has the root element . Her sub-elements to be So essentially the browser reads the data in the HTML document, something similar:
And, arranges them in a DOM structure like this:
The representation of each HTML element (and its content) in the DOM tree is known as a NodeThe root node is the node of . The DOM interface in JavaScript it is called document (since it is the representation of the HTML document). So we can access the DOM structure of an HTML document through the document interface in JavaScript. We can not only gain access, but also manipulate the HTML document via the DOM. We can add, delete and update elements on a web page. Every time we change or update nodes in the DOM tree, it is reflects on the web page
How nodes are designed
I said before that every bit of data from an HTML document is saved as an object in JavaScriptSo, how can the data stored as an object make sense as a boom be ranked? The nodes of a DOMboom have certain characteristics or properties. Almost any node in one boom has a parent node (the node right above it), child nodes (the nodes below it) and brothers and sisters (other nodes belonging to the same parent). Having this family above, below and around a node is what qualifies it as one part of one boom This family information of each node is stored as properties in the object that represents that nodeFor example, children is a property of a node that carries a list of the children of that node, so that the children are arranged logically under the node.
Avoid excessive DOM manipulation
As often as we find updating the DOM useful (to modify a web page), there is such a thing as exaggerate Suppose you have the color of a For example, say you want it add five additional rows to a tableFor each row, when the new nodes are created and added to the DOM, the boom is updated every time, to add up up to five updates in total. We can avoid this by using the DocumentFragment interface. Think of it as a box that could hold all five rows and are added to the boom. In this way are the five rows added as one piece of data and not one by one, leading to only one update in the tree structure. This happens not only when we delete or add elements, but resize an element can also affect other nodes, because the resized element may need other elements around it adjust their sizeThus, the corresponding nodes of all other elements must be updated and the HTML elements will be rendered again according to the new rules. Likewise, when the layout of a web page as a whole is affected, part or all of the web page can be displayed againThis process is known as ReplaceTo avoid excessive reflow make sure not to change the DOM too much. Changes to the DOM aren’t the only thing that Reflow can cause on a web page. Depending on the browser, other factors can also contribute.
Packing up up
Packing things up, the DOM is visualized as one boom made up of all elements found in an HTML document. Physically (as physical as anything digital can become), it is one set of nested JavaScript objects of which properties and methods contain the information that makes it possible log them into one boom
Document Object Model (DOM): Complete Guide: benefits
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