Javascript Query Selector

Michael Zippo 04.11.2021

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The two methods querySelector and getElementByID allow you to retrieve an element from the JavaScript Object Model DOM (Document) . However, each method has its own use cases.

In this guide, we look at the most common use case of querySelector and getElementById. We also compare these two methods and walk you through a basic example of how each of them work.

What is querySelector?

JavaScript querySelector () method allows you to retrieve a DOM element, or a web page, using a CSS selector. This method comes with a sister function called querySelectorAll () which selects all elements that match a particular DOM selector.

These two methods are incredibly versatile. This is because the CSS selector syntax allows you to select an element from a web page.

Using querySelector, you don’t have to worry about being limited by the ability to select items only for the or ID class , as you would if you used getElementById or getElementsByClassName. These methods are especially useful if the elements you select are similar to those you select in your CSS stylesheet.

Let’s take a look at the querySelector method. We’ll start by writing an HTML element that we can choose later in JavaScript:

We have defined a paragraph of text with the name of the class "accessibility". Then we select that paragraph using the querySelector ()

This code selects the first element whose class is equal to " accessibility". The "." means that we want to select a class. If we had two elements with the class "accessibility", we could use the querySelectorAll () to retrieve them both

What is getElementById?

getElementById () method gets an element based on its attribute ID, hence the name.

This method is more restrictive than querySelector because you cannot retrieve items based on their particular ID.

Use this option if you want to retrieve a single element from the web page. indeed, HTML ID must be unique for a particular element. You can not use a card of identity to refer to two elements on the Web page.

we will retrieve an element using the getElementById selector. First, we will write the HTML code from which we will choose an element:

We use the JavaScript instruction to retrieve the element whose ID is equal to "comments". This is the

element where we post comments on our web page.

The obvious similarity between these two methods is that the two elements of selecting a web page. They do it in different ways.

With a querySelector declaration, you can select an element based on a CSS selector. This means that you can select items by ID, class, or any other type of selector. Using the getElementById method, you cannot select an element based on its ID.

As a general rule, you should go for the selector that does the job most clearly.

If you just need to select an element by ID or class, you can use getElementById or getElementsByClassName, respectively. If you need to use a more elaborate rule to select items, the querySelector method is the best option

Both querySelector and getElementById have been part of JavaScript since a while. As a result, these methods are both fully supported on modern browsers.

Conclusion

The querySelector method allows you to retrieve an element using a CSS select query . The getElementById method retrieves an element by its DOM ID.

Both methods have broad browser support. You should choose to use querySelector if you need to select items using more complex rules that are easily representable using a CSS selector. If you want to select an element based on its ID, using getElementById is a good choice.

Now that you have the knowledge to know when to use the querySelector and getElementByID methods like a pro!

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Javascript Query Selector del: Questions

__del__

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 Query Selector del: Questions

__del__

How to delete a file or folder in Python?

5 answers

How do I delete a file or folder in Python?

2639

Answer #1

os.remove() removes a file.
os.rmdir() removes an empty directory.
shutil.rmtree() deletes a directory and all its contents.

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

pathlib.Path.unlink() removes a file or symbolic link.
pathlib.Path.rmdir() removes an empty directory.

We hope this article has helped you to resolve the problem. Apart from Javascript Query Selector, 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:

Carlo Chamberlet

California | 2023-03-23

Simply put and clear. Thank you for sharing. Javascript Query Selector and other issues with selectors Python module was always my weak point 😁. Will use it in my bachelor thesis

Manuel Richtgofen

New York | 2023-03-23

Thanks for explaining! I was stuck with Javascript Query Selector for some hours, finally got it done 🤗. Will use it in my bachelor thesis

Dmitry Danburry

Boston | 2023-03-23

Simply put and clear. Thank you for sharing. Javascript Query Selector and other issues with select Python module was always my weak point 😁. Will use it in my bachelor thesis