Improve your JavaScript skills: Understand what selectors do and when to use them

Improve your JavaScript skills: Be familiar with the characteristics and applicable scenarios of various selectors. Specific code examples are required

Introduction:
With the development of web development With the widespread application of JavaScript, selectors have become one of the essential skills for developers. Selectors can easily control and operate elements in HTML documents, allowing us to accurately select and operate specific elements as needed. This article will introduce common selectors, their characteristics and applicable scenarios, and provide specific code examples to help you better master this important skill.

1. Basic selector:

1. Selector based on ID (document.getElementById): Select elements based on their ID attributes and return a unique element object .
   Code example:

   let element = document.getElementById('myId');

   Applicable scenario: This selector can be used when we need to operate a specific element and the element has a unique ID attribute.

2. Selector based on tag name (document.getElementsByTagName): Select elements based on their tag names and return an array of element objects.
   Code example:

   let elements = document.getElementsByTagName('div');

   Applicable scenario: When we need to select one or more elements with the same tag name, we can use this selector.

3. Selector based on class name (document.getElementsByClassName): Selects elements based on their class name and returns an array of element objects.
   Code example:

   let elements = document.getElementsByClassName('myClass');

   Applicable scenario: This selector can be used when we need to select one or more elements with the same class name.

2. Advanced selector:

1. Attribute selector (querySelector): Selects elements based on their attributes and returns the selected element. An element object.
   Code example:

   let element = document.querySelector('input[type=text]');

   Applicable scenario: This selector can be used when we need to select elements with specific attributes or attribute values.

2. Selector similar to CSS selector (querySelectorAll): Select elements according to syntax similar to CSS selector and return an array of element objects.
   Code example:

   let elements = document.querySelectorAll('.myClass');

   Applicable scenario: This selector can be used when we need to select elements according to complex CSS selector rules.

3. Selectors combined with other attributes:

1. Child element selector (parentNode.children): Select the direct children of an element Element, returns an array of element objects.
   Code example:

   let parentElement = document.getElementById('parent');
   let elements = parentElement.children;

   Applicable scenario: When we need to select the direct child elements of an element, we can use this selector.

2. Descendant element selector (querySelectorAll): Selects all descendant elements of an element and returns an array of element objects.
   Code example:

   let elements = document.querySelectorAll('#parent span');

   Applicable scenario: When we need to select all descendant elements of an element, we can use this selector.

4. Advanced usage:

1. Pseudo-class selector: Add pseudo-classes based on the selector, which can be based on special conditions Select element.
   Code example:

   let element = document.querySelector('a:hover');

   Applicable scenario: This selector can be used when we need to select an element when the mouse is hovering over it.

2. Subsequent sibling selector (nextSibling): Selects all adjacent sibling elements after an element (excluding itself).
   Code example:

   let siblings = element.nextSibling;

   Applicable scenario: When we need to select adjacent sibling elements after an element, we can use this selector.

3. Parent element selector (parentNode): Select the direct parent element of an element.
   Code example:

   let parentElement = element.parentNode;

   Applicable scenario: When we need to select the direct parent element of an element, we can use this selector.

Summary:
By becoming familiar with and understanding the characteristics and applicable scenarios of various selectors, we can select and operate elements in HTML documents more accurately. Selectors are an indispensable and important skill in JavaScript development. Through continuous practice and learning, we can improve our JavaScript skills and develop web applications more efficiently. I hope the code examples provided in this article can help you better master the use of selectors and further improve your JavaScript skills.

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