What do querySelectorAll and getElementsBy* methods return?

Javascript Getelementsbyclassname Dom Traversal

When working with JavaScript and DOM manipulation, you may come across methods like getElementsByClassName, getElementsByTagName, and querySelectorAll. These methods are used to select elements from the DOM based on certain criteria, such as class name, tag name, or CSS selector.

getElementById vs getElementsBy*

Before diving into the details of these methods, let's briefly understand the difference between getElementById and getElementsBy* methods like getElementsByClassName and getElementsByTagName.

getElementById is a method that returns a single element with the specified ID. It is commonly used when you have unique IDs assigned to specific elements in your HTML document. Here's an example:

const elementById = document.getElementById('myIdElement');
elementById.style.color = 'red';

On the other hand, getElementsBy* methods return a collection of elements that match the specified criteria. These methods accept a string argument representing the class name, tag name, or CSS selector for the elements you want to select. Here's an example using getElementsByClassName:

const elementsByClassName = document.getElementsByClassName('myElement');
for(let i = 0; i < elementsByClassName.length; i++) {
    elementsByClassName[i].style.color = 'red';
}

As you can see, getElementsByClassName returns an HTMLCollection (a live collection of elements), which you can iterate through using a loop.

querySelectorAll

querySelectorAll is a more advanced and versatile method that allows you to select elements based on a CSS selector. It returns a NodeList containing all the selected elements. Here's an example:

const nodeList = document.querySelectorAll('.myElement');
nodeList.forEach(element => {
    element.style.color = 'red';
});

Like the getElementsBy* methods, querySelectorAll returns a collection of elements that you can iterate through using methods like forEach.

Summary

  • getElementById returns a single element with the specified ID.
  • getElementsBy* methods return a collection of elements that match the specified criteria.
  • querySelectorAll returns a NodeList containing all the selected elements.

So, to answer your initial question, getElementsByClassName and similar methods do not work exactly the same as getElementById. They return collections of elements that you need to iterate through to perform operations on each element.

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