querySelectorAll and getElementsBy* are two methods used to select elements from the DOM (Document Object Model) in JavaScript.
1) querySelectorAll: The querySelectorAll method returns a non-live NodeList of all elements matching a CSS selector within the document. The returned NodeList is a static collection of elements and is not updated when the DOM is updated.
Here’s an example of using querySelectorAll to select all p elements in the document:
const paragraphs = document.querySelectorAll('p');
2) getElementsBy: The getElementsBy* methods return live HTMLCollection of elements that match a specific tag name or class name. The returned HTMLCollection is updated automatically when the DOM is updated.
Here’s an example of using getElementsByTagName to select all p elements in the document:
const paragraphs = document.getElementsByTagName('p');
Here’s an example of using getElementsByClassName to select all elements with the class .example:
const elements = document.getElementsByClassName('example');
In general, querySelectorAll is preferred over getElementsBy* methods for performance and flexibility, as it allows you to use more advanced CSS selectors to select elements from the DOM. However, getElementsBy* methods are still widely used, especially for simple use cases like selecting elements by tag name or class name.