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Querying elements

document.querySelector() and document.querySelectorAll() are JavaScript functions that allow you to select elements on a web page using CSS selectors.

document.querySelector() is used to select the first element that matches the provided CSS selector. It returns the first matching element or null if no matching element is found.

Here's an example of how you can use it:

const firstButton = document.querySelector("button");

This will select the first button element on the page and store it in the variable firstButton.

document.querySelectorAll() is used to select all elements that match the provided CSS selector. It returns a NodeList (a collection of elements) that can be accessed and manipulated like an array.

Here's an example of how you can use it:

const buttons = document.querySelectorAll("button");

This will select all button elements on the page and store them in the variable "buttons".

Both functions can be used to access and manipulate the elements in the web page. Here's an example on how you can use it to extract the text of all buttons.

const buttons = document.querySelectorAll("button");
const buttonTexts = buttons.forEach(button => button.textContent);

It's important to note that when using querySelectorAll() in a browser environment, it returns a live NodeList, which means that if the DOM changes, the NodeList will also change.