


Author: ybcola
This js code was written a long time ago, probably a year ago! The problem I encountered at that time was when I was building a rural talent management system, because the system required selection and adding provinces, cities, counties, and even townships and villages through the background, and when modifying talent information, it required using a drop-down list to select. , and the source of each talent may be a province or city, or a province, city, or county, or you have to choose when you choose a team! At that time, my first reaction was to find out if there was any ready-made code on the Internet. The most commonly used one I found was provincial and municipal level two linkage. At that time, that js code could be seen everywhere on the Internet, but it was useless to me because I needed it. It is a code that is multi-level and can be expanded freely! In the end, I wrote the JS code myself.
In order to consider using it in multiple places on the same page, they were designed using the idea of objects. In order to realize the different contents of each multi-level linkage, the internal data structure was separated from the program, so Design the final calling method such as:
var city=new LightManAddressTree;
city.selectshow(obj,0); //obj is the dom node to be added,
if any The html code is as follows
Then the calling method should be
obj=document.getElementById("abc");
var city=new LightManAddressTree;
city.selectshow(obj,0);
In this way, the multi-level linkage content is displayed at the position within the closed div tag
The js design code is as follows:
//Start defining address data
var AddressTree={};
AddressTree["a_row"]=new Array(); //存所有记录
with(AddressTree){
a_row["1"]=["北京市",0,1];
a_row["2"]=["上海市",0,1];
a_row["3"]=["天津市",0,1];
a_row["4"]=["重庆市",0,1];
a_row["5"]=["河北",0,0];
a_row["6"]=["山西",0,0];
a_row["7"]=["内蒙古",0,0];
a_row["8"]=["辽宁",0,0];
a_row["9"]=["吉林",0,0];
a_row["10"]=["黑龙江",0,0];
a_row["11"]=["江苏",0,0];
a_row["12"]=["渐江",0,0];
a_row["13"]=["安徽",0,0];
a_row["14"]=["福建",0,0];
a_row["15"]=["江西",0,0];
a_row["16"]=["山东",0,0];
a_row["17"]=["河南",0,0];
a_row["18"]=["湖北",0,0];
a_row["19"]=["湖南",0,0];
a_row["20"]=["广东",0,0];
a_row["21"]=["广西",0,0];
a_row["22"]=["海南",0,0];
a_row["23"]=["四川",0,0];
a_row["24"]=["贵州",0,0];
a_row["25"]=["云南",0,0];
a_row["26"]=["西藏",0,0];
a_row["27"]=["陕西",0,0];
a_row["28"]=["甘肃",0,0];
a_row["29"]=["青海",0,0];
a_row["30"]=["宁夏",0,0];
a_row["31"]=["新壃",0,0];
a_row["32"]=["香港",0,1];
a_row["33"]=["澳门",0,1];
a_row["34"]=["台湾",0,0];
a_row["35"]=["石家庄",5,1];
a_row["36"]=["唐山",5,1];
a_row["37"]=["秦皇岛",5,1];
a_row["38"]=["邯郸",5,1];
a_row["39"]=["邢台",5,1];
a_row["40"]=["保定",5,1];
a_row["41"]=["张家口",5,1];
a_row["42"]=["承德",5,1];
a_row["43"]=["沧州",5,1];
a_row["44"]=["廊坊",5,1];
a_row["45"]=["衡水",5,1];
a_row["46"]=["太原",6,1];
a_row["47"]=["大同",6,1];
a_row["48"]=["阳泉",6,1];
a_row["49"]=["长治",6,1];
a_row["50"]=["晋城",6,1];
a_row["51"]=["朔州",6,1];
a_row["52"]=["晋中",6,1];
a_row["53"]=["运城",6,1];
a_row["54"]=["忻州",6,1];
a_row["55"]=["临汾",6,1];
a_row["56"]=["吕梁",6,1];
a_row["58"]=["呼和浩特",7,1];
a_row["59"]=["包头",7,1];
a_row["60"]=["乌海",7,1];
a_row["61"]=["赤峰",7,1];
a_row["62"]=["通辽",7,1];
a_row["63"]=["鄂尔多斯",7,1];
a_row["64"]=["呼伦贝尔",7,1];
a_row["65"]=["乌兰察布市",7,1];
a_row["66"]=["锡林郭勒盟",7,1];
a_row["67"]=["巴彦淖尔盟",7,1];
a_row["68"]=["阿拉善盟",7,1];
a_row["69"]=["兴安盟",7,1];
a_row["70"]=["沈阳",8,1];
a_row["71"]=["大连",8,1];
a_row["72"]=["鞍山",8,1];
a_row["73"]=["抚顺",8,1];
a_row["74"]=["本溪",8,1];
a_row["75"]=["丹东",8,1];
a_row["76"]=["锦州",8,1];
a_row["77"]=["葫芦岛",8,1];
a_row["78"]=["营口",8,1];
a_row["79"]=["盘锦",8,1];
a_row["80"]=["阜新",8,1];
a_row["81"]=["辽阳",8,1];
a_row["82"]=["铁岭",8,1];
a_row["83"]=["朝阳",8,1];
a_row["84"]=["长春",9,1];
a_row["85"]=["吉林",9,1];
a_row["86"]=["四平",9,1];
a_row["87"]=["辽源",9,1];
a_row["88"]=["通化",9,1];
a_row["89"]=["白山",9,1];
a_row["90"]=["松原",9,1];
a_row["91"]=["白城",9,1];
a_row["92"]=["延办朝鲜族自治州",9,1];
a_row["93"]=["哈尔滨",10,1];
a_row["94"]=["齐齐哈尔",10,1];
a_row["95"]=["鹤岗",10,1];
a_row["96"]=["双鸭山",10,1];
a_row["97"]=["鸡西",10,1];
a_row["98"]=["大庆",10,1];
a_row["99"]=["伊春",10,1];
a_row["100"]=["牡丹江",10,1];
a_row["101"]=["佳木斯",10,1];
a_row["102"]=["七台河",10,1];
a_row["103"]=["黑河",10,1];
a_row["104"]=["绥化",10,1];
a_row["105"]=["大兴安岭",10,1];
a_row["106"]=["南京",11,1];
a_row["107"]=["无锡",11,1];
a_row["108"]=["徐州",11,1];
a_row["109"]=["常州",11,1];
a_row["110"]=["苏州",11,1];
a_row["111"]=["南通",11,1];
a_row["112"]=["连云港",11,1];
a_row["113"]=["淮安",11,1];
a_row["114"]=["盐城",11,1];
a_row["115"]=["扬州",11,1];
a_row["116"]=["镇江",11,1];
a_row["117"]=["泰州",11,1];
a_row["118"]=["宿迀",11,1];
a_row["119"]=["杭州",12,1];
a_row["120"]=["宁波",12,1];
a_row["121"]=["温州",12,1];
a_row["122"]=["嘉兴",12,1];
a_row["123"]=["湖州",12,1];
a_row["124"]=["绍兴",12,1];
a_row["125"]=["金华",12,1];
a_row["126"]=["舟山",12,1];
a_row["127"]=["台州",12,1];
a_row["128"]=["丽水",12,1];
a_row["129"]=["衢州",12,1];
a_row["130"]=["合肥",13,1];
a_row["131"]=["芜湖",13,1];
a_row["132"]=["蚌埠",13,1];
a_row["133"]=["淮南",13,1];
a_row["134"]=["马鞍山",13,1];
a_row["135"]=["淮北",13,1];
a_row["136"]=["铜陵",13,1];
a_row["137"]=["安庆",13,1];
a_row["138"]=["黄山",13,1];
a_row["139"]=["滁州",13,1];
a_row["140"]=["阜阳",13,1];
a_row["141"]=["宿州",13,1];
a_row["142"]=["巢湖",13,1];
a_row["143"]=["六安",13,1];
a_row["144"]=["毫州",13,1];
a_row["145"]=["池州",13,1];
a_row["146"]=["宣城",13,1];
a_row["147"]=["福州",14,1];
a_row["148"]=["厦门",14,1];
a_row["149"]=["莆田",14,1];
a_row["150"]=["三明",14,1];
a_row["151"]=["泉州",14,1];
a_row["152"]=["漳州",14,1];
a_row["153"]=["南平",14,1];
a_row["154"]=["龙岩",14,1];
a_row["155"]=["宁德",14,1];
a_row["156"]=["南昌",15,1];
a_row["157"]=["景德镇",15,1];
a_row["158"]=["萍乡",15,1];
a_row["159"]=["新余",15,1];
a_row["160"]=["九江",15,1];
a_row["161"]=["鹰潭",15,1];
a_row["162"]=["吉安",15,1];
a_row["163"]=["宜春",15,1];
a_row["164"]=["抚州",15,1];
a_row["165"]=["上饶",15,1];
a_row["166"]=["赣州",15,1];
a_row["167"]=["济南",16,1];
a_row["168"]=["青岛",16,1];
a_row["169"]=["淄博",16,1];
a_row["170"]=["枣庄",16,1];
a_row["171"]=["东营",16,1];
a_row["172"]=["潍坊",16,1];
a_row["173"]=["烟台",16,1];
a_row["174"]=["威海",16,1];
a_row["175"]=["济宁",16,1];
a_row["176"]=["泰安",16,1];
a_row["177"]=["日照",16,1];
a_row["178"]=["莱芜",16,1];
a_row["179"]=["德州",16,1];
a_row["180"]=["临沂",16,1];
a_row["181"]=["聊城",16,1];
a_row["182"]=["滨州",16,1];
a_row["183"]=["菏泽",16,1];
a_row["184"]=["郑州",17,1];
a_row["185"]=["开封",17,1];
a_row["186"]=["洛阳",17,1];
a_row["187"]=["平顶山",17,1];
a_row["188"]=["焦作",17,1];
a_row["189"]=["鹤壁",17,1];
a_row["190"]=["新乡",17,1];
a_row["191"]=["安阳",17,1];
a_row["192"]=["濮阳",17,1];
a_row["193"]=["许昌",17,1];
a_row["194"]=["漯河",17,1];
a_row["195"]=["三门峡",17,1];
a_row["196"]=["南阳",17,1];
a_row["197"]=["南丘",17,1];
a_row["198"]=["信阳",17,1];
a_row["199"]=["周口",17,1];
a_row["200"]=["驻马店",17,1];
a_row["201"]=["济源",17,1];
a_row["202"]=["武汉",18,1];
a_row["203"]=["黄石",18,1];
a_row["204"]=["襄樊",18,1];
a_row["205"]=["十堰",18,1];
a_row["206"]=["荆州",18,1];
a_row["207"]=["宜昌",18,1];
a_row["208"]=["荆门",18,1];
a_row["209"]=["鄂州",18,1];
a_row["210"]=["孝感",18,1];
a_row["211"]=["黄冈",18,1];
a_row["212"]=["咸宁",18,1];
a_row["213"]=["随州",18,1];
a_row["214"]=["仙桃",18,1];
a_row["215"]=["天门",18,1];
a_row["216"]=["潜江",18,1];
a_row["217"]=["神农架",18,1];
a_row["218"]=["恩施土家族自治州",18,1];
a_row["219"]=["长沙",19,1];
a_row["220"]=["株洲",19,1];
a_row["221"]=["湘潭",19,1];
a_row["222"]=["衡阳",19,1];
a_row["223"]=["邵阳",19,1];
a_row["224"]=["岳阳",19,1];
a_row["225"]=["常德",19,1];
a_row["226"]=["张家界",19,1];
a_row["227"]=["益阳",19,1];
a_row["228"]=["郴州",19,1];
a_row["229"]=["怀化",19,1];
a_row["230"]=["娄底",19,1];
a_row["231"]=["湘西土家族苗族自治州",19,1];
a_row["232"]=["广州",20,1];
a_row["233"]=["深圳",20,1];
a_row["234"]=["珠海",20,1];
a_row["235"]=["汕头",20,1];
a_row["236"]=["韶关",20,1];
a_row["237"]=["佛山",20,1];
a_row["238"]=["江门",20,1];
a_row["239"]=["湛江",20,1];
a_row["240"]=["茂名",20,1];
a_row["241"]=["肇庆",20,1];
a_row["242"]=["惠州",20,1];
a_row["243"]=["梅州",20,1];
a_row["244"]=["汕尾",20,1];
a_row["245"]=["河源",20,1];
a_row["246"]=["阳江",20,1];
a_row["247"]=["清远",20,1];
a_row["248"]=["东莞",20,1];
a_row["249"]=["中山",20,1];
a_row["250"]=["潮州",20,1];
a_row["251"]=["揭阳",20,1];
a_row["252"]=["云浮",20,1];
a_row["253"]=["南宁",21,1];
a_row["254"]=["柳州",21,1];
a_row["255"]=["桂林",21,1];
a_row["256"]=["梧州",21,1];
a_row["257"]=["北海",21,1];
a_row["258"]=["防城港",21,1];
a_row["259"]=["钦州",21,1];
a_row["260"]=["贵港",21,1];
a_row["261"]=["玉林",21,1];
a_row["262"]=["百色",21,1];
a_row["263"]=["贺州",21,1];
a_row["264"]=["河池",21,1];
a_row["265"]=["来宾",21,1];
a_row["266"]=["崇左",21,1];
a_row["267"]=["海口",22,1];
a_row["268"]=["三亚",22,1];
a_row["269"]=["五指山",22,1];
a_row["270"]=["琼海",22,1];
a_row["271"]=["儋州",22,1];
a_row["272"]=["文昌",22,1];
a_row["273"]=["方宁",22,1];
a_row["274"]=["东方",22,1];
a_row["275"]=["澄迈",22,1];
a_row["276"]=["定安",22,1];
a_row["277"]=["屯昌",22,1];
a_row["278"]=["临高",22,1];
a_row["279"]=["白沙黎族自治县",22,1];
a_row["280"]=["江黎族自治县",22,1];
a_row["281"]=["乐东黎族自治县",22,1];
a_row["282"]=["陵水黎族自治县",22,1];
a_row["283"]=["保亭黎族苗族自治县",22,1];
a_row["284"]=["琼中称许苗族自治县",22,1];
a_row["285"]=["成都",23,1];
a_row["286"]=["自贡",23,1];
a_row["287"]=["攀枝花",23,1];
a_row["288"]=["泸州",23,1];
a_row["289"]=["德阳",23,1];
a_row["290"]=["Mianyang",23,1];
a_row["291"]=["Guangyuan",23,1];
a_row["292"]=["Suining ",23,1];
a_row["293"]=["Neijiang",23,1];
a_row["294"]=["Leshan",23,1];
a_row["295"]=["Nanchong",23,1];
a_row["296"]=["Yibin",23,1];
a_row["297"]=["Guang'an ",23,1];
a_row["298"]=["Dazhou",23,1];
a_row["299"]=["Meishan",23,1];
a_row["300"]=["Ya'an",23,1];
a_row["301"]=["Bazhong",23,1];
a_row["302"]=[" Ziyang",23,1];
a_row["303"]=["Aba Tibetan and Qiang Autonomous Prefecture",23,1];
a_row["304"]=["Ganzi Tibetan Autonomous Prefecture",23, 1];
a_row["305"]=["Liangshan Yi Autonomous Prefecture",23,1];
a_row["306"]=["Guiyang",24,1];
a_row[ "307"]=["Liupanshui",24,1];
a_row["308"]=["Zunyi",24,1];
a_row["309"]=["Anshun", 24,1];
a_row["310"]=["Tongren",24,1];
a_row["311"]=["Bijie",24,1];
a_row[ "312"]=["Qiandongnan Buyi and Miao Autonomous Prefecture",24,1];
a_row["313"]=["Qiandongnan Miao Autonomous Prefecture",24,1];
a_row["314 "]=["Qiannan Buyi and Miao Autonomous Prefecture",24,1];
a_row["315"]=["Kunming",25,1];
a_row["316"]=[" Qujing",25,1];
a_row["317"]=["Yuxi",25,1];
a_row["318"]=["Baoshan",25,1];
a_row["319"]=["Zhaotong",25,1];
a_row["320"]=["Lijiang",25,1];
a_row["321"]=[" Simao",25,1];
a_row["322"]=["Jiancang",25,1];
a_row["323"]=["Wenshan Zhuang and Miao Autonomous Prefecture",25,1 ];
a_row["324"]=["Honghe Hani and Yi Autonomous Prefecture",25,1];
a_row["325"]=["Xishuangbanna Dai Autonomous Prefecture",25,1];
a_row["326"]=["Chuxiong Yi Autonomous Prefecture",25,1];
a_row["327"]=["Dali Bai Autonomous Prefecture",25,1];
a_row["328" ]=["Dehong Dai and Jingpo Autonomous Prefecture",25,1];
a_row["329"]=["Nujiang Lisu Autonomous Prefecture",25,1];
a_row["330"] =["Diqing Tibetan Autonomous Prefecture",25,1];
a_row["331"]=["Lhasa",26,1];
a_row["332"]=["Nagqu",26 ,1];
a_row["333"]=["Chamdo",26,1];
a_row["334"]=["Shannan",26,1];
a_row[" 335"]=["Shigatse",26,1];
a_row["336"]=["Ali",26,1];
a_row["337"]=["Lingzhi",26 ,1];
a_row["338"]=["Xi'an",27,1];
a_row["339"]=["Tongchuan",27,1];
a_row[" 340"]=["Baoji",27,1];
a_row["341"]=["Xianyang",27,1];
a_row["342"]=["Weinan",27 ,1];
a_row["343"]=["Yan'an",27,1];
a_row["344"]=["Hanzhong",27,1];
a_row[" 345"]=["Yulin",27,1];
a_row["346"]=["Ankang",27,1];
a_row["347"]=["Shangluo",27 ,1];
a_row["348"]=["Lanzhou",28,1];
a_row["349"]=["Jinchang",28,1];
a_row[" 350"]=["silver",28,1];
a_row["351"]=["Tianshui",28,1];
a_row["352"]=["Jiayuguan",28 ,1];
a_row["353"]=["Wuwei",28,1];
a_row["354"]=["Zhangye",28,1];
a_row[" 355"]=["Pingliang",28,1];
a_row["356"]=["Saquan",28,1];
a_row["357"]=["Qingyang" ,28,1];
a_row["358"]=["Dingxi",28,1];
a_row["359"]=["Longnan",28,1];
a_row ["360"]=["Linxia Hui Autonomous Prefecture",28,1];
a_row["361"]=["Gannan Tibetan Autonomous Prefecture",28,1];
a_row["362"]= ["Xining",29,1];
a_row["363"]=["Haidong",29,1];
a_row["364"]=["Haibei Tibetan Autonomous Prefecture",29, 1];
a_row["365"]=["Huangnan Tibetan Autonomous Prefecture",29,1];
a_row["366"]=["Hainan Tibetan Autonomous Prefecture",29,1];
a_row["367"]=["Goluo Tibetan Autonomous Prefecture",29,1];
a_row["368"]=["Yushu Tibetan Autonomous Prefecture",29,1];
a_row["369 "]=["Hai Mongolian Tibetan Autonomous Prefecture",29,1];
a_row["370"]=["Yinchuan",30,1];
a_row["371"]=["Shizuishan ",30,1];
a_row["372"]=["Wuzhong",30,1];
a_row["373"]=["Guyuan",30,1];
a_row["374"]=["Urumqi",31,1];
a_row["375"]=["Karamay",31,1];
a_row["376"]=["Shihezi ",31,1];
a_row["377"]=["Alar",31,1];
a_row["378"]=["Tumushuk",31,1] ;
a_row["379"]=["Wujiaqu",31,1];
a_row["380"]=["Tulu",31,1];
a_row[" 381"]=["Hami",31,1];
a_row["382"]=["Hotian",31,1];
a_row["383"]=["Aksu",31 ,1];
a_row["384"]=["Kashgar",31,1];
a_row["385"]=["Kizilsu Kirgiz Autonomous Prefecture",31,1];
a_row["386"]=["Bayingoleng Mongolian Autonomous Prefecture",31,1];
a_row["387"]=["Changji Hui Autonomous Prefecture",31,1];
a_row ["388"]=["Bortala Mongolian Autonomous Prefecture",31,1];
a_row["389"]=["Ili Kazakh Autonomous Prefecture",31,1];
a_row["390 "]=["Taipei",34,1];
a_row["391"]=["Kaohsiung",34,1];
a_row["392"]=["Keelung",34, 1];
a_row["393"]=["Taichung",34,1];
a_row["394"]=["Tainan",34,1];
a_row["395 "]=["Hsinchu",34,1];
a_row["396"]=["Chiayi",34,1];
a_row["397"]=["sss",285, 1];
}
var j=0;
AddressTree["a_record"]=new Array();//Storage record number
for(i in AddressTree["a_row"] ){AddressTree["a_record"][j ]=i;}
AddressTree.ObjNumber=1;
//Address selection constructor
function LightManAddressTree(){
var Data = AddressTree; //Data record data variable
this.noselectshow=["- -Please select a province--","--Please select a city--","--Please select a district or county--"];//Do not select display values at each level
this.grade=0; //Grade Number
this.idvalue=0; //The id number of the address selection value
this.text=""; //Address string
this.listseparator=" "; //In the address string Delimiter symbol
this.selectName="a_tree" (AddressTree.ObjNumber ) "_";
//End of defining address data
this.getfontpath = function(id){ //Get the superior of the specified record number Path
var path = "",upid;
try{
upid=(isNaN(id)?0:id);
while(upid!=0){
var upid= Data["a_row"][upid][1];
If(path!="")path=upid "," path;else path=upid;
}
}
catch( e){};
return eval("[" path "]");
}
//Create the following list
this.selectshowlevel=function(obj,upid,def){
var selectobj,optionobj,havedef;
selectobj=document.getElementById(this.selectName this.grade);
if(selectobj){
document.getElementById(this.selectName this.grade).options. length=0;
}else{
selectobj=document.createElement("select");
selectobj.id=this.selectName this.grade;
selectobj.grade=this.grade;
selectobj.obj=this;
selectobj.onchange=function(){
if(this.options[this.selectedIndex].value!=""){
this.obj.selectshow(obj ,this[this.selectedIndex].value); .obj.grade-1;i ){
var df=document.getElementById(this.obj.selectName i);
df.options.length=0;
defaultoption(this.obj,df, i);
🎜> }
defaultoption(this,selectobj, this.grade);
//Display data at level
if(upid>=0){
for(var j=0;j thisrecord=Data["a_row"][Data["a_record"][j]];
if(thisrecord[1]==upid){
optionobj=document.createElement("option");
optionobj.text=thisrecord[0];
optionobj.value=Data["a_record"][j];
selectobj.options.add(optionobj);
if(def==Data ["a_record"][j]) havedef=true;
}
}
}
if(havedef)selectobj.value=def;
return selectobj;
}
this.selectshow = function(obj,id){ //显示选中记录号
var selectobj,optionobj,thisrecord;
var lastgrade,tempid=id,tempgrade;
var fontpath=this.getfontpath(id);
tempgrade=this.grade;
this.grade=0;
//显示选中前部分内容
for (var i=0;i
if(i
else
this.Add(obj,this.selectshowlevel(obj,fontpath[i],id));
}
this.grade ;
}
//显示选中后部分内容
do{
lastgrade=this.selectshowlevel(obj,tempid);
tempid=lastgrade.value;
if (tempid=="")tempid=-1;
this.Add(obj,lastgrade);
this.grade ;
}
while(lastgrade.options.length>0);
//删除多余选项
for(i=this.grade-1;i
}
//最得值
getvalue(this);
}
this.Add=function(obj,s){
if(s.options.length>0&&!document.getElementById(s.id))obj.appendChild(s);
}
//获取选择值
function getvalue(obj){
var sel
obj.text="";
obj.idvalue=0;
for(var i=0;i
if(sel.value!=""){
obj.text =(obj.text.match("\S")==null?"":obj.listseparator) sel.options[sel.selectedIndex].text;
obj.idvalue=sel.options[sel.selectedIndex].value;
}else{break;}
}
}
//级别显示数据
function defaultoption(obj,sobj,g){
try{
if(obj.noselectshow[g]){
optionobj=document.createElement("option");
optionobj.text=obj.noselectshow[g];
optionobj.value="";
sobj.options.add(optionobj,0);
}
}
catch(e){}
}
}
address_test.htm
HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<script></script>

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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