Course Introduction：This article provides a solution for pre-selecting an item in a drop-down box based on a database value using HTML and PHP. The main issue addressed is the incorrect setting of the selected attribute on the select element. The article offers correcte
2024-10-21 comment 0 1250
Course Introduction：Core points jQuery provides a variety of methods to manipulate drop-down boxes, including adding, removing, and changing options using methods such as append(), remove() and val(). Be sure to use the $() function to select the drop-down box before applying any method. To get the current value of the selected option, use the val() method. You can use the text() method to get the text of the selected option. Multiple values ??can be retrieved using the each() function. The onChange event in jQuery can be used to identify the selected options in the drop-down box. This event triggers a function that looks for the text of the selected option. Introduction Operating the drop-down box in jQuery requires
2025-03-05 comment 0 1129
Course Introduction：In web development, creating drop-down lists using HTML5 mainly depends on select and option tags. 1. Basic structure: define options by defining the drop-down box; 2. Add default selections: Use selected attribute to set the default options; 3. Group display options: use the classification of options; 4. Optional advanced functions: realize multiple selection through multiple, and control the number of display options through size. These tips can improve form clarity and user experience.
2025-07-19 comment 0 499
Course Introduction：The most direct way to make the input box in the HTML form required is to use the required property. This property is a Boolean type, and no value is required. It can be used to verify it on the input, select or textarea tags, such as:; Common matching types include text, email, password, etc.; for checkbox, directly add required to force check; in the radio button group, just add required to the first option; the select drop-down box needs to set the default empty value option to trigger verification; different browsers may have different styles and contents of prompt information. If a unified prompt effect is required, you can customize it with JavaScript or third-party libraries for customization.
2025-07-07 comment 0 778
Course Introduction：To prevent Notepad from automatically adding .txt extensions, wrap the file name in quotes when saving and select All Files in the Save Type drop-down menu. The specific steps are as follows: 1. Enter a quoted name in the file name field of the "Save As" dialog box, such as "config"; 2. Select "All Files" from the "Save Type" drop-down menu to disable the behavior of automatically adding extensions; 3. Note that Windows may hide known extensions. You can check "File Name Extension" in the "View" tab of File Explorer to confirm that the saving is correct. Follow these steps to ensure that Notepad saves files in the specified format without automatically adding the default .txt extension.
2025-07-13 comment 0 405
Course Elementary 13776
Course Introduction：Scala Tutorial Scala is a multi-paradigm programming language, designed to integrate various features of object-oriented programming and functional programming.
Course Elementary 82285
Course Introduction："CSS Online Manual" is the official CSS online reference manual. This CSS online development manual contains various CSS properties, definitions, usage methods, example operations, etc. It is an indispensable online query manual for WEB programming learners and developers! CSS: Cascading Style Sheets (English full name: Cascading Style Sheets) is an application used to express HTML (Standard Universal Markup Language).
Course Elementary 13145
Course Introduction：SVG is a markup language for vector graphics in HTML5. It maintains powerful drawing capabilities and at the same time has a very high-end interface to operate graphics by directly operating Dom nodes. This "SVG Tutorial" is intended to allow students to master the SVG language and some of its corresponding APIs, combined with the knowledge of 2D drawing, so that students can render and control complex graphics on the page.
Course Elementary 24591
Course Introduction：In the "AngularJS Chinese Reference Manual", AngularJS extends HTML with new attributes and expressions. AngularJS can build a single page application (SPAs: Single Page Applications). AngularJS is very easy to learn.
Course Elementary 27450
Course Introduction：Go is a new language, a concurrent, garbage-collected, fast-compiled language. It can compile a large Go program in a few seconds on a single computer. Go provides a model for software construction that makes dependency analysis easier and avoids most C-style include files and library headers. Go is a statically typed language, and its type system has no hierarchy. Therefore users do not need to spend time defining relationships between types, which feels more lightweight than typical object-oriented languages. Go is a completely garbage-collected language and provides basic support for concurrent execution and communication. By its design, Go is intended to provide a method for constructing system software on multi-core machines.
javascript - Is there a plug-in for multi-select drop-down grouping based on vue?
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javascript - Please tell me about the second-level linkage ideas, without plug-ins! ! !
2017-05-19 10:22:20 0 5 673
