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How to fetch API data with js?

How to fetch API data with js?

There are three main ways to get data from the API using JavaScript. First, use the fetch function built in the browser, which is suitable for simple GET requests. Pay attention to URL correctness, CORS support and error handling; second, combine async/await writing to make the asynchronous logic clearer and easier to maintain, but consider the compatibility of old browsers; third, use the axios library, which has more powerful functions, supports automatic JSON conversion, cancel requests, etc., and is suitable for complex projects. In addition, common problems such as cross-domain restrictions, JSON format errors, cache impact, etc. can be solved by setting response headers, trying/catch capture, adding random parameters, etc. It is recommended to debug with the developer tool Network panel.

Jun 27, 2025 am 12:42 AM
api
How to properly clear an interval set by setInterval?

How to properly clear an interval set by setInterval?

The way to completely clear the setInterval timer in JavaScript is to save the timer ID and call clearInterval(). 1. The unique ID returned by setInterval must be obtained and saved, otherwise it cannot be cleared; 2. Use clearInterval (timerId) to stop the specified timer, and repeated calls have no effect; 3. Before creating a new timer, you should check and clear the existing timer to prevent overlapping operation; 4. In frameworks such as React, Vue, etc., the timer needs to be cleaned when uninstalling components to avoid errors.

Jun 27, 2025 am 12:24 AM
What is 'this' keyword in js?

What is 'this' keyword in js?

In JavaScript, the value of this depends on the function call method rather than the location of the definition. The main rules are as follows: 1. In ordinary functions, if called independently, this points to the global object; 2. When called as an object method, this points to the object; 3. Use .call(), .apply() or .bind() to specify this manually; 4. The arrow function does not have this itself, and it inherits this in the outer scope; 5. Common traps include losing context in callbacks, this disorder in event processing, and the constructor not using new to cause errors. It can be solved through .bind(), arrow function or ensuring the use of new. After mastering these rules, this behavior will be clearer and easier to understand.

Jun 27, 2025 am 12:24 AM
How to manipulate the DOM with js?

How to manipulate the DOM with js?

Operating DOM is the foundation of front-end development, and mastering its core methods and precautions is the key to achieving web page interaction. When getting elements, document.getElementById(), document.querySelector() and document.querySelectorAll() are commonly used. The first two are used to obtain a single element through ID and obtain the first matching element through CSS selector respectively, while querySelectorAll returns a static NodeList; note that getElementsByClassName and getElementsByTagName return a dynamic collection. Modify content and

Jun 27, 2025 am 12:19 AM
dom
A server-side JS roundup for getting started with Node.js and Express

A server-side JS roundup for getting started with Node.js and Express

After installing Node.js and npm, run npminit-y and install Express; 2. Create an app.js file, use the express module to create a server instance and define a port; 3. Use app.get() and other methods to set up a route; 4. Use app.listen() to start the server; 5. Use nodemon to automatically restart the server; 6. Use express.json() to parse the JSON request body; 7. Use express.Router() to organize the route; 8. Use Mongoose or Sequelize to connect to the database; 9. Use dotenv to manage environment variables. This article introduces how to build Exp from scratch

Jun 27, 2025 am 12:12 AM
What is the difference between clientHeight, offsetHeight, and scrollHeight?

What is the difference between clientHeight, offsetHeight, and scrollHeight?

clientHeight measures the visible content area plus inner margin of the element, offsetHeight includes content, inner margin and border, scrollHeight contains all content height (including invisible parts); 1.clientHeight is used to obtain the height of the actual visible area of ​​the element on the screen, without borders and overflow content; 2. offsetHeight reflects the complete dimensions of the element in the layout, including borders but not margins; 3. scrollHeight provides the height of the entire content, suitable for judging overflow or automatic scrolling scenes; the three are suitable for different measurement needs, and are selected according to whether the borders or overflow content is needed.

Jun 27, 2025 am 12:10 AM
What is the nullish coalescing operator (??)?

What is the nullish coalescing operator (??)?

The ?? operator solves the problem that when setting the default value using ||, it may incorrectly exclude valid values ​​such as 0, empty string or false. It only returns the right-side default value when the left side is null or undefined, and does not exclude other false values. For example: itemCount??5 will use 5 when itemCount is null or undefined, but if it is 0 or empty string, the original value will be retained. Usage scenarios include handling user input, optional object properties, etc. that require precise control, and use ||? should be preferred at this time. In addition, brackets should be used in complex expressions to avoid operator priority issues.

Jun 26, 2025 am 12:54 AM
Null value merge operator
How can you reduce the payload size of a JavaScript application?

How can you reduce the payload size of a JavaScript application?

If JavaScript applications load slowly and have poor performance, the problem is that the payload is too large. Solutions include: 1. Use code splitting (CodeSplitting), split the large bundle into multiple small files through React.lazy() or build tools, and load it as needed to reduce the first download; 2. Remove unused code (TreeShaking), use the ES6 module mechanism to clear "dead code" to ensure that the introduced libraries support this feature; 3. Compress and merge resource files, enable Gzip/Brotli and Terser to compress JS, reasonably merge files and optimize static resources; 4. Replace heavy-duty dependencies and choose lightweight libraries such as day.js and fetch

Jun 26, 2025 am 12:54 AM
What is the Shadow DOM?

What is the Shadow DOM?

TheShadowDOMsolvestheproblemofstyleandmarkupconflictsonwebpagesbyenablingscoped,encapsulatedDOMtrees.Withoutit,globalCSSstylescanunintentionallyaffectelementsacrossthepage,especiallyinlargeapplicationsorwhenusingthird-partywidgets.ByattachingahiddenD

Jun 26, 2025 am 12:53 AM
How to get query string parameters from the URL in JavaScript?

How to get query string parameters from the URL in JavaScript?

Getting query parameters in URLs can be implemented in JavaScript through URLSearchParams or manually parsing. Using URLSearchParams is a recommended method for modern browsers. After obtaining the query string through window.location.search, use newURLSearchParams() to parse it, and operate parameters through .get(), .has(), .getAll() and other methods; if it is compatible with old browsers or hash routing scenarios, you can manually parse it, extract the query string from the URL and press & to split the key-value pairs, and then press = to split it one by one and store it into the object; for the case of repeated parameter names, .getAll(

Jun 26, 2025 am 12:53 AM
What are common js security vulnerabilities like XSS?

What are common js security vulnerabilities like XSS?

JavaScript security vulnerabilities mainly include XSS, CSRF, third-party dependency vulnerabilities and sensitive information leakage. 1.XSS steals data by injecting malicious scripts, and should use HTML escape and framework protection; 2. CSRF automatically submits requests using cookies, and the backend needs to set SameSite and verify the source; 3. Third-party library vulnerabilities can be detected and updated through npmaudit; 4. Sensitive information leakage should avoid storing keys on the frontend and closing debug output.

Jun 26, 2025 am 12:52 AM
What is the difference between target and currentTarget in a JavaScript event?

What is the difference between target and currentTarget in a JavaScript event?

In JavaScript, event.target is the actual element that triggers the event, and event.currentTarget is the element that binds the event handler. Specifically: 1. event.target points to the DOM element that triggered the event initially, regardless of where the event listener is located; 2. event.currentTarget always points to the element that attaches the event listener, and is not affected by the event starting point; 3. Use event.target to identify specific child elements that are clicked in the event delegation, while using event.currentTarget to ensure that the parent element of the bound event is operated.

Jun 26, 2025 am 12:51 AM
event
What is optional chaining (?.) and what problem does it solve?

What is optional chaining (?.) and what problem does it solve?

Optionalchaining(?.)inJavaScriptallowsyoutosafelyaccessdeeplynestedobjectpropertieswithoutexplicitlycheckingeachreferenceinthechain,preventingerrorswhenencounteringnullorundefined.1.Iteliminates“Cannotreadpropertyofundefined”errorsbyreturningundefine

Jun 26, 2025 am 12:49 AM
What is the difference between default and named exports?

What is the difference between default and named exports?

Defaultexportsallowonemainvaluepermodulewithflexiblenamingonimport,whilenamedexportsenablemultiplespecificexportsrequiringexactnames.Namedexportsareidealformultipleutilitiesneedingclearidentification,defaultexportssuitsinglefocusedexportslikecomponen

Jun 26, 2025 am 12:49 AM
default exports

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