search
HomeWeb Front-endJS TutorialExample of use of getAttribute method in js_javascript skills

getAttribute() method

So far, we have introduced you to two methods of retrieving specific element nodes: one is to use the getElementById() method, and the other is to use the getElementsByTagName() method. After finding that element, we can use the getAttribute() method to query the values ​​of its various attributes.
The getAttribute() method is a function. It has only one parameter - the name of the attribute you want to query:
object.getAttribute(attribute)
However, the getAttribute() method cannot be called through the document object, unlike the other methods we have introduced before. We can only call it through an element node object.
For example, you can combine it with the getElementsByTagName() method to query the title attribute of each

element, as follows:

var text=document.getElementsByTagName("p")
for (var i=0;i<text.length;i++)
{
alert(text[i].getAttribute("title"));
}

If you insert the above code at the end of the "Shopping List" example document given earlier, and reload the page in a web browser, a text message "a gentle reminder" will pop up on the screen. alter dialog box.
There is only one

element with a title attribute in the "Shopping List" document. If this document also has one or more

elements without a title attribute, the corresponding getAttribute("title") call will return null. null is the null value in the JavaScript language, which means "the thing you are talking about does not exist." If you want to verify this for yourself, first insert the following text into your Shopping List document after the existing text paragraph:

This is just test


Then reload the page. This time, you will see two alter dialog boxes, and the second dialog box will be blank or just display the word "null" - depending on how your web browser displays null values.
We can modify our script so that it only pops up a message when the title attribute exists. We will add an if statement to check if the return value of the getAttribute() method is null. Taking advantage of this opportunity, we also added a few variables to improve the readability of the script:
var ts=document.getElementsByTagName("li");
for (var i=0; i<ts.length;i++)
{text=ts[i].getAttribute("title");
if(text!=null)
{
alert(text)
}
}

Now, if you reload this page, you will only see an alter dialog box with the message "a gentle reminder" as shown below.
We can even make this code shorter. When checking whether an item of data is null, we are actually checking whether it exists. This check can be simplified by directly using the data being checked as the condition of the if statement. if (something) is completely equivalent to if (something != null), but the former is obviously more concise. At this point, if something exists, the condition of the if statement will be true; if something does not exist, the condition of the if statement will be false.
Specific to this example, as long as we replace if (title_text != null) with if (title_text), we can get a more concise code. In addition, in order to further increase the readability of the code, we can also take this opportunity to write the alter statement and the if statement on the same line, which can make them closer to the English sentences in our daily life:

var ts=document.getElementsByTagName("li");
for (var i=0; i<ts.length;i++)
{text=ts[i].getAttribute("title");
if(text) alert(text)
}

3.4.2 setAttribute() method
All the methods we have introduced to you before can only be used to retrieve information. The setAttribute() method has one essential difference from them: it allows us to modify the value of the attribute node.
Similar to the getAttribute() method, the setAttribute() method is also a function that can only be called through the element node object, but the setAttribute() method requires us to pass it two parameters:
obiect.setAttribute(attribute,value)
In the following example, the first statement will retrieve the element whose id attribute value is purchase, and the second statement will set the title attribute value of this element to a list of goods:

var shopping=document.getElementById("purchases")
shopping.setAttribute("title","a list of goods")

We can use the getAttribute() method to prove that the value of the title attribute of this element has indeed changed:

var shopping=document.getElementById("purchases");
alert(shopping.getAttribute("title"));
shopping.setAttribute("title","a list of goods");
alert(shopping.getAttribute("title"));

The above statements will pop up two alert dialog boxes on the screen: the first alter dialog box appears before the setAttribute() method is called, it will be blank or display the word "null"; the second one appears After the title attribute value is set, it will display the "a list of goods" message.
In the above example, we set the title attribute of an existing node, but this attribute did not originally exist. This means that the setAttribute() call we issued actually completed two operations: first created the attribute, and then set its value. If we use the setAttribute() method on an existing attribute of an element node, the current value of this attribute will be overwritten.
In the "Shopping List" example document, the

element already has a title attribute whose value is a gentle reminder. We can use the setAttribute() method to change its current value:

<script type="text/javascript">
var ts=document.getElementsByTagName("li");
for (var i=0; i<ts.length;i++)
{
var text=ts[i].getAttribute("title");
alert(ts[i].getAttribute("title"))
if(text)
{
ts[i].setAttribute("title","我会成功!")
alert(ts[i].getAttribute("title"))
}
}

The above code will first retrieve all

elements with title attributes from the document, and then modify all their title attribute values ​​​​to brand new title text. Specific to the "Shopping List" document, the attribute value a gentle reminder will be overridden.
There is a detail worthy of attention here: modifications to the document through the setAttribute() method will cause corresponding changes in the display effect and/or behavior of the document in the browser window, but when we use the browser's view When you view the source code of a document using the source option, you will still see the original attribute values ​​- that is, changes made by the setAttribute() method will not be reflected in the source code of the document itself. This phenomenon of "inconsistency between appearance and inside" comes from the working mode of the DOM: first load the static content of the document, and then refresh them dynamically. Dynamic refresh does not affect the static content of the document. This is the true power and allure of the DOM: refreshing page content does not require the end user to perform a page refresh operation in their browser.

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
JavaScript and the Web: Core Functionality and Use CasesJavaScript and the Web: Core Functionality and Use CasesApr 18, 2025 am 12:19 AM

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.

Understanding the JavaScript Engine: Implementation DetailsUnderstanding the JavaScript Engine: Implementation DetailsApr 17, 2025 am 12:05 AM

Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.

Python vs. JavaScript: The Learning Curve and Ease of UsePython vs. JavaScript: The Learning Curve and Ease of UseApr 16, 2025 am 12:12 AM

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python vs. JavaScript: Community, Libraries, and ResourcesPython vs. JavaScript: Community, Libraries, and ResourcesApr 15, 2025 am 12:16 AM

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

From C/C   to JavaScript: How It All WorksFrom C/C to JavaScript: How It All WorksApr 14, 2025 am 12:05 AM

The shift from C/C to JavaScript requires adapting to dynamic typing, garbage collection and asynchronous programming. 1) C/C is a statically typed language that requires manual memory management, while JavaScript is dynamically typed and garbage collection is automatically processed. 2) C/C needs to be compiled into machine code, while JavaScript is an interpreted language. 3) JavaScript introduces concepts such as closures, prototype chains and Promise, which enhances flexibility and asynchronous programming capabilities.

JavaScript Engines: Comparing ImplementationsJavaScript Engines: Comparing ImplementationsApr 13, 2025 am 12:05 AM

Different JavaScript engines have different effects when parsing and executing JavaScript code, because the implementation principles and optimization strategies of each engine differ. 1. Lexical analysis: convert source code into lexical unit. 2. Grammar analysis: Generate an abstract syntax tree. 3. Optimization and compilation: Generate machine code through the JIT compiler. 4. Execute: Run the machine code. V8 engine optimizes through instant compilation and hidden class, SpiderMonkey uses a type inference system, resulting in different performance performance on the same code.

Beyond the Browser: JavaScript in the Real WorldBeyond the Browser: JavaScript in the Real WorldApr 12, 2025 am 12:06 AM

JavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.

Building a Multi-Tenant SaaS Application with Next.js (Backend Integration)Building a Multi-Tenant SaaS Application with Next.js (Backend Integration)Apr 11, 2025 am 08:23 AM

I built a functional multi-tenant SaaS application (an EdTech app) with your everyday tech tool and you can do the same. First, what’s a multi-tenant SaaS application? Multi-tenant SaaS applications let you serve multiple customers from a sing

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
Will R.E.P.O. Have Crossplay?
1 months agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Atom editor mac version download

Atom editor mac version download

The most popular open source editor