


Detailed explanation of jquery operation select (including adding, deleting, clearing, value taking, etc.)
1. Select the item whose value is pxx.
$(".selector").val("pxx");
2. Select the item whose text is pxx.
$(".selector").find("option[text='pxx']").attr("selected",true);
Here is a usage of square brackets. The equal sign in parentheses is preceded by the attribute name without quotation marks. Many times, the use of square brackets can make logic very simple.
3. Get the value of the currently selected item
$(".selector").val();
4. Get the text of the currently selected item
$(".selector").find("option:selected").text();
The colon is used here. Mastering its usage and drawing inferences about other cases will also help The code becomes concise.
The cascade of selects is often used, that is, the value of the second select changes with the value selected by the first select. This is very simple in jquery.
$(".selector1").change(function(){ // 先清空第二个 $(".selector2").empty(); // 实际的应用中,这里的option一般都是用循环生成多个了 var option = $("<option>").val(1).text("pxx"); $(".selector2").append(option); });
jQuery gets the Text and Value selected by Select:
Syntax explanation:
$("#select_id").change(function(){//code...}); //为Select添加事件,当选择其中一项时触发 var checkText=$("#select_id").find("option:selected").text(); //获取Select选择的Text var checkValue=$("#select_id").val(); //获取Select选择的Value var checkIndex=$("#select_id ").get(0).selectedIndex; //获取Select选择的索引值 var maxIndex=$("#select_id option:last").attr("index"); //获取Select最大的索引值
jQuery sets the Text and Value selected by Select:
Syntax explanation:
$("#select_id ").get(0).selectedIndex=1; //设置Select索引值为1的项选中 $("#select_id ").val(4); // 设置Select的Value值为4的项选中 $("#select_id option[text='jQuery']").attr("selected", true); //设置Select的Text值为jQuery的项选中
jQuery adds/Deletes the Option item of Select:
Syntax explanation:
$("#select_id").append("<option value='Value'>Text</option>"); //为Select追加一个Option(下拉项) $("#select_id").prepend("<option value='0'>请选择</option>"); //为Select插入一个Option(第一个位置) $("#select_id option:last").remove(); //删除Select中索引值最大Option(最后一个) $("#select_id option[index='0']").remove(); //删除Select中索引值为0的Option(第一个) $("#select_id option[value='3']").remove(); //删除Select中Value='3'的Option $("#select_id option[text='4']").remove(); //删除Select中Text='4'的Option
jquery radio value, checkbox value, select value, radio selected, checkbox selected , select selected, and related
Get the value of a set of radio selected items
var item = $('input[name=items][checked]').val();
Get the selected item The text of the selected item
var item = $("select[name=items] option[selected]").text();
The second element of the select drop-down box is the currently selected value
$( '#select_id')[0].selectedIndex = 1;
The second element of the radio radio selection group is the currently selected value
$('input[name=items]').get(1).checked = true;
Get value:
Text box, text area: $("#txt").attr("value");
Multiple selection box checkbox: $("#checkbox_id").attr ("value");
Radio selection group radio: $("input[type=radio][checked]").val();
Drop-down box select: $('#sel').val( );
Control form elements:
Text box, text area: $("#txt").attr("value",'');//Clear content
$("#txt") .attr("value",'11');//Fill content
Multiple selection box checkbox: $("#chk1").attr("checked",'');//Uncheck
$("#chk2").attr("checked",true);//Check
if($("#chk1").attr('checked')==undefined) //Determine whether it has been checked Check
Radio selection group radio: $("input[type=radio]").attr("checked",'2');//Set the item with value=2 as the currently selected item
Drop-down box select : $("#sel").attr("value",'-sel3');//Set the item with value=-sel3 as the currently selected item
$("").appendTo("#sel")//Add the option of the drop-down box
$("#sel").empty( ); //Clear the drop-down box
The above is the detailed content of Detailed explanation of jquery operation select (including adding, deleting, clearing, value taking, etc.). For more information, please follow other related articles on the PHP Chinese website!

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

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 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 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 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.

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.

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.

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.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

WebStorm Mac version
Useful JavaScript development tools

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

SublimeText3 English version
Recommended: Win version, supports code prompts!