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jquery.select.js
/*
Ajax three-level linkage
Date: 2013-2-26
settings parameter description
-----
firstUrl: first-level drop-down data acquisition URL , josn returns
firstValue: default first-level drop-down value
secondUrl: second-level drop-down data acquisition URL, josn returns
secondValue: default second-level drop-down value
thirdUrl: third-level drop-down data acquisition URL, josn Return
thirdValue: default three-level drop-down value
nodata: no data status
required: required option
--------------------- --------- */
(function($){
$.fn.linkSelect=function(settings){
if($(this).size()//Default value
settings=$.extend({
firstUrl:"js/city.min.js",
firstValue:null,
secondValue: null,
thirdValue:null,
nodata:null,
required:true
},settings);
var box_obj=this;
var first_obj=box_obj.find(". first");
var second_obj=box_obj.find(".second");
var third_obj=box_obj.find(".third");
var select_prehtml=(settings.required) ? "" : "";
var prepareSelectHtml=function(jsonArray){
var temp_html=select_prehtml;
$.each(jsonArray,function( index,row){
temp_html ="";
});
return temp_html;
};
//Assign the secondary drop-down box function
var secondStart=function(){
second_obj.empty().attr("disabled",true);
third_obj.empty( ).attr("disabled",true);
if(first_obj.val()==''){
return;
}
$.getJSON(settings.secondUrl, { firstValue: first_obj.val(), time: new Date().getTime() }, function(jsonResult){
if(!jsonResult.success){
if(settings.nodata=="none"){
second_obj.css("display","none");
third_obj.css("display","none");
}else if(settings.nodata=="hidden"){
second_obj.css("visibility","hidden");
third_obj.css("visibility","hidden");
};
return;
}
// Traverse Assign secondary drop-down list
second_obj.html(prepareSelectHtml(jsonResult.data)).attr("disabled",false).css({"display":"","visibility":""});
thirdStart();
});
};
// Assign the third-level drop-down box function
var thirdStart=function(){
third_obj.empty().attr ("disabled",true);
$.getJSON(settings.thirdUrl, { firstValue: first_obj.val(),secondValue:second_obj.val(), time: new Date().getTime() }, function( jsonResult){
if(!jsonResult.success){
if(settings.nodata=="none"){
third_obj.css("display","none");
}else if(settings.nodata=="hidden"){
third_obj.css("visibility","hidden");
};
return;
}
// Traverse assignment three Level drop-down list
third_obj.html(prepareSelectHtml(jsonResult.data)).attr("disabled",false).css({"display":"","visibility":""});
thirdStart ();
});
};
var init=function(){
// Traverse the assignment one-level drop-down list
$.getJSON(settings.firstUrl, {time: new Date().getTime() }, function(jsonResult){
if(!jsonResult.success){
return;
}
// Traverse the assigned one-level drop-down list
first_obj. html(prepareSelectHtml(jsonResult.data));
secondStart();
// If the first and second level values are passed in, select them. (setTimeout is set for compatibility with IE6)
setTimeout(function(){
if(settings.firstValue && settings.firstValue.length>0){
first_obj.val(settings.firstValue);
secondStart();
setTimeout(function(){
if(settings.secondValue && settings.secondValue.length>0){
second_obj.val(settings.secondValue);
thirdStart();
setTimeout(function(){
if(settings.thirdValue && settings.thirdValue.length>0){
third_obj.val(settings.thirdValue);
};
},1 );
};
},1);
};
},1);
});
// Event occurs when level one is selected
first_obj. bind("change",function(){
secondStart();
});
// An event occurs when the second level is selected
second_obj.bind("change",function(){
thirdStart();
});
};
//Initialize the first drop-down box
init();
};
})(jQuery);
${rc.contextPath}/repair/loadCategory The corresponding background method and return json value:
@RequestMapping("loadCategory")
@ResponseBody
public Map
String msg = "";
boolean isSuccess = false;
List
效果如图:


JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

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.


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