Built-in Date function
var mydate = new Date();
mydate.getYear(); //Get the current year (2 digits)
mydate.getFullYear(); //Get the complete year (4 digits, 1970- ????)
mydate.getMonth(); //Get the current month (0-11, 0 represents January)
mydate.getDate(); //Get the current day (1-31)
mydate.getDay() ; //Get the current week Number (0-23)
mydate.getMinutes(); //Get the current number of minutes (0-59)
mydate.getSeconds(); //Get the current number of seconds (0-59)
mydate.getMilliseconds(); / /Get the current milliseconds (0-999)
mydate.toLocaleDateString(); //Get the current date
var mytime=mydate.toLocaleTimeString(); //Get the current time
mydate.toLocaleString( ); //Get the date and time
Extension function
Date.prototype.isLeapYear Determine leap year
Date.prototype.Format Date formattingDate.prototype.DateAdd Date calculation
Date.prototype.DateDiff Compare date difference
Date.prototype.toString Convert date to string
Date.prototype.toArray Split the date into an array
Date.prototype.DatePart Get part of the date information
Date.prototype.MaxDayOfDate Get the maximum number of days in the month where the date is
Date.prototype.WeekNumOfYear Determine the week of the year where the date is
StringToDate character Convert date type
IsValidDate to verify date validity
CheckDateTime complete date and time check
daysBetween date and number of days difference
//--------------------------------------------------- // 判断闰年 //--------------------------------------------------- Date.prototype.isLeapYear = function() { return (0==this.getYear()%4&&((this.getYear()%100!=0)||(this.getYear()%400==0))); } //--------------------------------------------------- // 日期格式化 // 格式 YYYY/yyyy/YY/yy 表示年份 // MM/M 月份 // W/w 星期 // dd/DD/d/D 日期 // hh/HH/h/H 时间 // mm/m 分钟 // ss/SS/s/S 秒 //--------------------------------------------------- Date.prototype.Format = function(formatStr) { var str = formatStr; var Week = ['日','一','二','三','四','五','六']; str=str.replace(/yyyy|YYYY/,this.getFullYear()); str=str.replace(/yy|YY/,(this.getYear() % 100)>9?(this.getYear() % 100).toString():'0' + (this.getYear() % 100)); str=str.replace(/MM/,this.getMonth()>9?this.getMonth().toString():'0' + this.getMonth()); str=str.replace(/M/g,this.getMonth()); str=str.replace(/w|W/g,Week[this.getDay()]); str=str.replace(/dd|DD/,this.getDate()>9?this.getDate().toString():'0' + this.getDate()); str=str.replace(/d|D/g,this.getDate()); str=str.replace(/hh|HH/,this.getHours()>9?this.getHours().toString():'0' + this.getHours()); str=str.replace(/h|H/g,this.getHours()); str=str.replace(/mm/,this.getMinutes()>9?this.getMinutes().toString():'0' + this.getMinutes()); str=str.replace(/m/g,this.getMinutes()); str=str.replace(/ss|SS/,this.getSeconds()>9?this.getSeconds().toString():'0' + this.getSeconds()); str=str.replace(/s|S/g,this.getSeconds()); return str; } //+--------------------------------------------------- //| 求两个时间的天数差 日期格式为 YYYY-MM-dd //+--------------------------------------------------- function daysBetween(DateOne,DateTwo) { var OneMonth = DateOne.substring(5,DateOne.lastIndexOf ('-')); var OneDay = DateOne.substring(DateOne.length,DateOne.lastIndexOf ('-')+1); var OneYear = DateOne.substring(0,DateOne.indexOf ('-')); var TwoMonth = DateTwo.substring(5,DateTwo.lastIndexOf ('-')); var TwoDay = DateTwo.substring(DateTwo.length,DateTwo.lastIndexOf ('-')+1); var TwoYear = DateTwo.substring(0,DateTwo.indexOf ('-')); var cha=((Date.parse(OneMonth+'/'+OneDay+'/'+OneYear)- Date.parse(TwoMonth+'/'+TwoDay+'/'+TwoYear))/86400000); return Math.abs(cha); } //+--------------------------------------------------- //| 日期计算 //+--------------------------------------------------- Date.prototype.DateAdd = function(strInterval, Number) { var dtTmp = this; switch (strInterval) { case 's' :return new Date(Date.parse(dtTmp) + (1000 * Number)); case 'n' :return new Date(Date.parse(dtTmp) + (60000 * Number)); case 'h' :return new Date(Date.parse(dtTmp) + (3600000 * Number)); case 'd' :return new Date(Date.parse(dtTmp) + (86400000 * Number)); case 'w' :return new Date(Date.parse(dtTmp) + ((86400000 * 7) * Number)); case 'q' :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number*3, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds()); case 'm' :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds()); case 'y' :return new Date((dtTmp.getFullYear() + Number), dtTmp.getMonth(), dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds()); } } //+--------------------------------------------------- //| 比较日期差 dtEnd 格式为日期型或者 有效日期格式字符串 //+--------------------------------------------------- Date.prototype.DateDiff = function(strInterval, dtEnd) { var dtStart = this; if (typeof dtEnd == 'string' )//如果是字符串转换为日期型 { dtEnd = StringToDate(dtEnd); } switch (strInterval) { case 's' :return parseInt((dtEnd - dtStart) / 1000); case 'n' :return parseInt((dtEnd - dtStart) / 60000); case 'h' :return parseInt((dtEnd - dtStart) / 3600000); case 'd' :return parseInt((dtEnd - dtStart) / 86400000); case 'w' :return parseInt((dtEnd - dtStart) / (86400000 * 7)); case 'm' :return (dtEnd.getMonth()+1)+((dtEnd.getFullYear()-dtStart.getFullYear())*12) - (dtStart.getMonth()+1); case 'y' :return dtEnd.getFullYear() - dtStart.getFullYear(); } } //+--------------------------------------------------- //| 日期输出字符串,重载了系统的toString方法 //+--------------------------------------------------- Date.prototype.toString = function(showWeek) { var myDate= this; var str = myDate.toLocaleDateString(); if (showWeek) { var Week = ['日','一','二','三','四','五','六']; str += ' 星期' + Week[myDate.getDay()]; } return str; } //+--------------------------------------------------- //| 日期合法性验证 //| 格式为:YYYY-MM-DD或YYYY/MM/DD //+--------------------------------------------------- function IsValidDate(DateStr) { var sDate=DateStr.replace(/(^\s+|\s+$)/g,''); //去两边空格; if(sDate=='') return true; //如果格式满足YYYY-(/)MM-(/)DD或YYYY-(/)M-(/)DD或YYYY-(/)M-(/)D或YYYY-(/)MM-(/)D就替换为'' //数据库中,合法日期可以是:YYYY-MM/DD(2003-3/21),数据库会自动转换为YYYY-MM-DD格式 var s = sDate.replace(/[\d]{ 4,4 }[\-/]{ 1 }[\d]{ 1,2 }[\-/]{ 1 }[\d]{ 1,2 }/g,''); if (s=='') //说明格式满足YYYY-MM-DD或YYYY-M-DD或YYYY-M-D或YYYY-MM-D { var t=new Date(sDate.replace(/\-/g,'/')); var ar = sDate.split(/[-/:]/); if(ar[0] != t.getYear() || ar[1] != t.getMonth()+1 || ar[2] != t.getDate()) { //alert('错误的日期格式!格式为:YYYY-MM-DD或YYYY/MM/DD。注意闰年。'); return false; } } else { //alert('错误的日期格式!格式为:YYYY-MM-DD或YYYY/MM/DD。注意闰年。'); return false; } return true; } //+--------------------------------------------------- //| 日期时间检查 //| 格式为:YYYY-MM-DD HH:MM:SS //+--------------------------------------------------- function CheckDateTime(str) { var reg = /^(\d+)-(\d{ 1,2 })-(\d{ 1,2 }) (\d{ 1,2 }):(\d{ 1,2 }):(\d{ 1,2 })$/; var r = str.match(reg); if(r==null)return false; r[2]=r[2]-1; var d= new Date(r[1],r[2],r[3],r[4],r[5],r[6]); if(d.getFullYear()!=r[1])return false; if(d.getMonth()!=r[2])return false; if(d.getDate()!=r[3])return false; if(d.getHours()!=r[4])return false; if(d.getMinutes()!=r[5])return false; if(d.getSeconds()!=r[6])return false; return true; } //+--------------------------------------------------- //| 把日期分割成数组 //+--------------------------------------------------- Date.prototype.toArray = function() { var myDate = this; var myArray = Array(); myArray[0] = myDate.getFullYear(); myArray[1] = myDate.getMonth(); myArray[2] = myDate.getDate(); myArray[3] = myDate.getHours(); myArray[4] = myDate.getMinutes(); myArray[5] = myDate.getSeconds(); return myArray; } //+--------------------------------------------------- //| 取得日期数据信息 //| 参数 interval 表示数据类型 //| y 年 m月 d日 w星期 ww周 h时 n分 s秒 //+--------------------------------------------------- Date.prototype.DatePart = function(interval) { var myDate = this; var partStr=''; var Week = ['日','一','二','三','四','五','六']; switch (interval) { case 'y' :partStr = myDate.getFullYear();break; case 'm' :partStr = myDate.getMonth()+1;break; case 'd' :partStr = myDate.getDate();break; case 'w' :partStr = Week[myDate.getDay()];break; case 'ww' :partStr = myDate.WeekNumOfYear();break; case 'h' :partStr = myDate.getHours();break; case 'n' :partStr = myDate.getMinutes();break; case 's' :partStr = myDate.getSeconds();break; } return partStr; } //+--------------------------------------------------- //| 取得当前日期所在月的最大天数 //+--------------------------------------------------- Date.prototype.MaxDayOfDate = function() { var myDate = this; var ary = myDate.toArray(); var date1 = (new Date(ary[0],ary[1]+1,1)); var date2 = date1.dateAdd(1,'m',1); var result = dateDiff(date1.Format('yyyy-MM-dd'),date2.Format('yyyy-MM-dd')); return result; } //+--------------------------------------------------- //| 取得当前日期所在周是一年中的第几周 //+--------------------------------------------------- Date.prototype.WeekNumOfYear = function() { var myDate = this; var ary = myDate.toArray(); var year = ary[0]; var month = ary[1]+1; var day = ary[2]; document.write('< script language=VBScript\> \n'); document.write('myDate = DateValue(''+month+'-'+day+'-'+year+'') \n'); document.write('result = DatePart('ww', myDate) \n'); document.write(' \n'); return result; } //+--------------------------------------------------- //| 字符串转成日期类型 //| 格式 MM/dd/YYYY MM-dd-YYYY YYYY/MM/dd YYYY-MM-dd //+--------------------------------------------------- function StringToDate(DateStr) { var converted = Date.parse(DateStr); var myDate = new Date(converted); if (isNaN(myDate)) { //var delimCahar = DateStr.indexOf('/')!=-1?'/':'-'; var arys= DateStr.split('-'); myDate = new Date(arys[0],--arys[1],arys[2]); } return myDate; }

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.


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