What are the js selectors?

Commonly used JavaScript selectors include "getElementById", "getElementsByClassName", "getElementsByTagName", "querySelector" and "querySelectorAll": 1. getElementById, selects elements through the ID attribute of the element, and returns the first matching one elements and so on.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

JavaScript selectors are used to select elements in HTML documents and operate on them. The following are commonly used JavaScript selectors:

1. getElementById:

   Selects an element by its ID attribute and returns the first matching element.

2. getElementsByClassName:

   Select elements by their class names and return an HTMLCollection containing all matching elements.

3. getElementsByTagName:

   Select elements by their tag names and return an HTMLCollection containing all matching elements.

4. querySelector:

   Select elements through the CSS selector and return the first matching element.

5. querySelectorAll:

   Select elements through a CSS selector and return a NodeList containing all matching elements.

These selectors can be used flexibly as needed. For example, if you want to select the element with the ID "myElement", you can use getElementById("myElement"); if you want to select all elements with the class name "myClass", you can use getElementsByClassName("myClass"); if you want to select For all paragraph elements, you can use getElementsByTagName("p"); if you want to select the first element with a class name of "myClass", you can use querySelector(".myClass"), etc.

It should be noted that getElementById selects elements with a unique ID for the entire document, while other selectors can select multiple matching elements. In addition, HTMLCollection and NodeList are both array-like objects, and the elements in them can be traversed through indexing or looping.

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