JavaScript is a scripting language widely used in web development. It can complete data operations, event processing, dynamic special effects and other operations. In JavaScript, the document object refers to the HTML document object in the web page. Through the document object, we can obtain the nodes, elements, attributes, etc. in the web page and operate the web page.
So, how to get the JavaScript document object? Below are some methods of obtaining JavaScript document objects to give you an in-depth understanding of this topic.
- document object
The document object in JS represents the current web page document. We can access elements in the web page document through the document object. This is also the most commonly used method of obtaining JavaScript document objects.
The document object contains two properties, document.documentElement and document.body, where document.documentElement represents the entire document and document.body represents the body node of the document. Through these two attributes, you can get the attributes and nodes of the entire web page. For example: document.documentElement.clientHeight and document.body.clientHeight can get the window height of the web page and the height of the entire document respectively.
- getElementById() method
The getElementById() method is a method to obtain elements through the ID attribute. It is one of the methods of the document object. If an element in the web page has an ID attribute set, the element can be obtained directly through the getElementById() method. For example: document.getElementById('divId') can obtain the element with the ID 'divId'.
- getElementsByTagName() method
The getElementsByTagName() method is a method to obtain elements based on their names. This method is also one of the methods of the document object. The getElementsByTagName() method can be used to obtain the collection of all specified elements in the web page. For example: document.getElementsByTagName('div') can obtain the collection of all div elements.
- getElementsByClassName() method
The getElementsByClassName() method is a method to obtain elements based on the class name. This method is also one of the methods of the document object. The getElementsByClassName() method can be used to obtain the collection of all elements with the specified class name in the web page. For example: document.getElementsByClassName('className') can obtain the collection of all elements with the class name 'className'.
- querySelector() and querySelectorAll() methods
querySelector() method is a method to obtain elements through CSS selectors. This method is also one of the methods of the document object. . It can get the first element in the web page that meets the requirements of the CSS selector. For example: document.querySelector('#divId') can get the first element that meets the ID of 'divId'.
querySelectorAll() method is an upgraded version of querySelector() method. It can obtain the collection of all elements in the web page that meet the CSS selector requirements. For example: document.querySelectorAll('.className') can obtain all classes. A collection of elements named 'className'.
- parentElement and children attributes
The parentElement and children attributes are node attributes, which can be used to obtain the parent element and child elements of the node. The parent element of the node can be obtained through the parentElement attribute. For example: node.parentElement can obtain the parent element of the node node. All child elements of the node can be obtained through the children attribute. For example: node.children can obtain the collection of all child elements of the node node.
To sum up, there are many ways to obtain JavaScript document objects. Common methods include document objects, getElementById() method, getElementsByTagName() method, getElementsByClassName() method, querySelector() method, querySelectorAll( ) method, parentElement attribute and children attribute, etc. Using these methods, you can quickly and easily obtain JavaScript document objects to operate and modify web pages.
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