Javascript Domain

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The JavaScript Document Object Model (DOM) is a representation of the HTML elements of a web page. It is an interface that we can use to manipulate a web page by modifying its content or style.

We can access the DOM by right clicking on a web page and selecting " inspect ". This way, a section (right or left) should appear with the HTML elements of the web page you are on. By hovering the mouse over these elements, you can find out which sections of the page are represented by them when the sections of the page are highlighted.

We can manipulate the content or the style of the pages by coding in the console.

The DOM itself is a tree-like data structure with nested parent and child elements. Items without children are called " leaves ‚". When you inspect a page, you can see that our main node element of our tree is the document, then our html tag, then our head tag, which contains the scripts and our title, which branch out into a single tree. We can also see our body tag, which is separate from the head tag and branches into a different tree that carries a different element. Below is an example of the elements used to represent the Python.Engineering home page.

capture of screen career-karma-honepage-to-HTML exposed elements

Note that the right part of the homepage is highlighted when hovering over a particular div element which is a child of the body tag . In this article, we discuss ways to select elements in the DOM for future manipulation.

Selecting elements in the DOM

There are two ways to select elements in the DOM. One uses getElements methods, the other uses querySelector methods.

getElement methods

The getElement methods take a single string argument of a tag name, class name, or identifier. The tag and class name will return an array-like object called an HTML collection indicating how many times the item you are looking for appears on the page.

document.getElementsByTagName (’p’): Note that there are currently seven p tags on the Python.Engineering homepage.

 capture of Python.Engineering home screen with code-a- console

document.getElementsByClassName ( ’hzjqne’) : this will return the HTML collection containing all the elements with the given class.

document.getElementById ( ’__ NEXT_DATA__’) : recovery of an element by the identifier the corresponding element da ns the console will be returned. Because ID names must be unique, they should not return a collection of anything.

capture of screen career-karma- home with code at the console

querySelector methods

When using the query select methods, we must remember to include the period before the class name and the pound sign before the identifying name to find or select what we are looking for. This is the most common error when using the querySelector () or querySelectorAll methods () .

 screenshot by -career-karma-pa ge of home console with code

Another difference is that when you use querySelectorAll () instead of an HTML library, you get in return something called a node list, which is also an array type object.

 screenshot -di- -karma home career with queues-in-console

The difference between an HTML gallery and a node list is that we can use the method .forEach () on a list of nodes. We cannot do this with an HTML collection if we are trying to manipulate the DOM. However, JavaScript has a method that we can use to create an array from an object of array type such as an HTML library or a node list. This method is .from () and comes from the Array class. Array.from (arrayLikeObject)

Note that we can select all the elements with querySelectors that we can with getMethods ().

Conclusion

The DOM is a powerful interface that represents the HTML code of a web page. It has a tree structure that we can see when we inspect the page. We can use methods like querySelector () or getMethods to be able to manipulate what we see with JavaScript.

👻 Read also: what is the best laptop for engineering students?

Javascript Domain __del__: Questions

How can I make a time delay in Python?

5 answers

I would like to know how to put a time delay in a Python script.

2973

Answer #1

import time
time.sleep(5)   # Delays for 5 seconds. You can also use a float value.

Here is another example where something is run approximately once a minute:

import time
while True:
    print("This prints once a minute.")
    time.sleep(60) # Delay for 1 minute (60 seconds).

2973

Answer #2

You can use the sleep() function in the time module. It can take a float argument for sub-second resolution.

from time import sleep
sleep(0.1) # Time in seconds

Javascript Domain __del__: Questions

How to delete a file or folder in Python?

5 answers

How do I delete a file or folder in Python?

2639

Answer #1


Path objects from the Python 3.4+ pathlib module also expose these instance methods:

We hope this article has helped you to resolve the problem. Apart from Javascript Domain, check other __del__-related topics.

Want to excel in Python? See our review of the best Python online courses 2023. If you are interested in Data Science, check also how to learn programming in R.

By the way, this material is also available in other languages:



Walter Sikorski

Shanghai | 2023-02-01

Thanks for explaining! I was stuck with Javascript Domain for some hours, finally got it done 🤗. Checked yesterday, it works!

Walter Gonzalez

Berlin | 2023-02-01

I was preparing for my coding interview, thanks for clarifying this - Javascript Domain in Python is not the simplest one. Checked yesterday, it works!

Oliver Innsbruck

Abu Dhabi | 2023-02-01

Maybe there are another answers? What Javascript Domain exactly means?. Will get back tomorrow with feedback

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