Does '.then(function(a){ return a; })' Actually Do Anything for Promises?

This article will introduce how to use JavaScript to achieve the effect of clicking on images. The core idea is to use HTML5's data-* attribute to store the alternate image path, and listen to click events through JavaScript, dynamically switch the src attributes, thereby realizing image switching. This article will provide detailed code examples and explanations to help you understand and master this commonly used interactive effect.

First, check whether the browser supports GeolocationAPI. If supported, call getCurrentPosition() to get the user's current location coordinates, and obtain the latitude and longitude values ​​through successful callbacks. At the same time, provide error callback handling exceptions such as denial permission, unavailability of location or timeout. You can also pass in configuration options to enable high precision, set the timeout time and cache validity period. The entire process requires user authorization and corresponding error handling.

To create a repetition interval in JavaScript, you need to use the setInterval() function, which will repeatedly execute functions or code blocks at specified milliseconds intervals. For example, setInterval(()=>{console.log("Execute every 2 seconds");},2000) will output a message every 2 seconds until it is cleared by clearInterval(intervalId). It can be used in actual applications to update clocks, poll servers, etc., but pay attention to the minimum delay limit and the impact of function execution time, and clear the interval in time when no longer needed to avoid memory leakage. Especially before component uninstallation or page closing, ensure that

This article aims to solve the problem of returning null when obtaining DOM elements through document.getElementById() in JavaScript. The core is to understand the script execution timing and DOM parsing status. By correctly placing the tag or utilizing the DOMContentLoaded event, you can ensure that the element is attempted again when it is available, effectively avoiding such errors.

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Nuxt3's Composition API core usage includes: 1. definePageMeta is used to define page meta information, such as title, layout and middleware, which need to be called directly in it and cannot be placed in conditional statements; 2. useHead is used to manage page header tags, supports static and responsive updates, and needs to cooperate with definePageMeta to achieve SEO optimization; 3. useAsyncData is used to securely obtain asynchronous data, automatically handle loading and error status, and supports server and client data acquisition control; 4. useFetch is an encapsulation of useAsyncData and $fetch, which automatically infers the request key to avoid duplicate requests

This tutorial explains in detail how to format numbers into strings with fixed two decimals in JavaScript, even integers can be displayed in the form of "#.00". We will focus on the use of the Number.prototype.toFixed() method, including its syntax, functionality, sample code, and key points to be noted, such as its return type always being a string.

Use the writeText method of ClipboardAPI to copy text to the clipboard, it needs to be called in security context and user interaction, supports modern browsers, and the old version can be downgraded with execCommand.