Application of JavaScript format string_javascript skills

After some design, this function was finally completed. After introducing this js, you can configure the format string yourself to output various customized date formats.

Flowchart

It can be seen that the so-called format string is actually a string containing specific characters, and then based on its actual The meaning is replaced with the specified value.
In this article, we only use the Date object as an example. In fact, the value of the format string goes beyond this. Under what circumstances can format strings be used? Hopefully you will find the answer by the end of this article.
Algorithm introduction
Below I will use an example to illustrate the format string algorithm. This example will format the "day" part of the date, such as 2008-8-8. If the format string is "d", it will output "8"; if the format string is "dd", it will output "08"; if If the format string is "dddd", "five" will be output; if the format string is "dddd", "friday" will be output. The parameter d is a Date object and format is a string:

Copy code The code is as follows:

//Format Day
function FormatDay(d, format){
while(format.indexOf("d") > -1){
var regex = /[d] /;
format = format.replace(regex,function(w){
switch(w.length){
case 0:break;
case 1:
return d.getDate();
case 2:
return d.getDate() < 10 ? "0" d.getDate() : d.getDate();
case 3:
switch(d.getDay()) {
case 0:
return "日";
case 1:
return "一";
case 2:
return "二";
case 3:
return "三";
case 4:
return "四";
case 5:
return "五";
case 6:
return "六";
}
default:
switch(d.getDay()){
case 0:
return "Sunday";
case 1:
return "Monday";
case 2:
return "Tuesday";
case 3:
return "Wednesday";
case 4:
return "Thursday";
case 5:
return "Friday";
case 6:
return "Saturday";
}
}
});
}
return format;
}

As you can see, the core part is:

Copy the code The code is as follows:

while (format.indexOf("d") > -1) {
var regex = /[d] /;
format = format.replace(regex, function(w) {
switch (w.length) {
case 0: break;
case 1:
//todo
case 2:
//todo
case 3:
/ /todo
case x:
//todo
default:
//todo
}
});
}

解释：
1. 使用while循环，只要格式字符串format中含有特定字符就一直执行下去；
2. 声明一个正则表达式对象/[x]+/，其中x表示特定字符；
3. 使用string对象的replace方法替换特定字符；
4. 根据匹配到的特定字符串的长度，执行不同的操作（在本示例中，“d”、“dd”、“ddd”代表不同的含义）。
格式字符串说明
以508-1-9 14:3:5为例

格式字符串	描述	示例
y	格式化年。年份由世纪+年代组成。	“y”输出8 “yy”输出08 “yyy”输出508 “yyyy”输出0508 “yyyyyy”输出000508
M	格式化月。	“M”输出1 “MM”输出01 “MMM”或更多输出一月
d	格式化日。	“d”输出9 “dd” 输出09 “ddd” 输出一 “dddd” 或更多输出星期一
H,h	格式化小时。其中H表示24小时制，h表示12小时制。	“H”输出14 “HH” 或更多输出14 “h”输出2 “hh” 或更多输出02
m	格式化分钟。	“m”输出3 “mm” 或更多输出03
s	格式化秒	“s”输出5 “ss” 或更多输出05

更多的设置，大家可以自己动手做一下。

示例
引用此js后，在浏览器的控制台中测试结果如下：

如何，有没有心动的感觉……

顺便说一下各浏览器的控制台呼出方式：

浏览器	快捷键
Chrome	Ctrl + Shift + J
IE8	F12
FireFox	忘了。FireFox中的控制台不是原生的，是一个叫FireBug的插件。

Source code
The following code can be downloaded from DateExtension.js

Copy the code The code is as follows:

Date.prototype.ToString = function(format){
if(typeof(format) == "string"){
return FormatDateTime(this, format);
}
return FormatDateTime(this, "yyyy-MM-dd HH:mm:ss");
}
//Format DateTime object
function FormatDateTime(d, format){
format = FormatYear( d, format);
format = FormatMonth(d, format);
format = FormatDay(d, format);
format = FormatHour(d, format);
format = FormatMinute(d, format);
format = FormatSecond(d, format);
return format;
}
//Format year
function FormatYear(d, format){
var fullYear = d.getFullYear(); //Full year
var century = Math.floor(fullYear / 100); //Century
var year = fullYear % 100; //Year
while(format.indexOf ("y") > -1){
var regex = /[y] /;
format = format.replace(regex,function(w){
//Format string if it is " y" or "yy", only the year is returned. Otherwise, the century year is returned.
switch(w.length){
case 0:break;
case 1:
return year;
case 2:
return year < 10 ? "0" year : year;
default:
var yearPart = year < 10 ? "0" year : year;
var centuryPart = "";
for(var i = 0; i < w.length - 2 - century.toString().length; i ){
centuryPart = "0";
}
centuryPart = century;
return centuryPart yearPart;
}
});
}
return format;
}
//Format month
function FormatMonth(d, format){
var month = d.getMonth() 1;
while(format.indexOf("M") > -1){
var regex = /[M] /;
format = format .replace(regex,function(w){
switch(w.length){
case 0:break;
case 1:
return month;
case 2:
return month < 10 ? "0" month : month;
default:
switch(month){
case 1:
return "January";
case 2:
return "February";
case 3:
return "March";
case 4:
return "April";
case 5:
return "May";
case 6:
return "June";
case 7:
return "July";
case 8:
return "August";
case 9 :
return "September";
case 10:
return "October";
case 11:
return "November";
case 12:
return "December";
}
}
});
}
return format;
}
//Format day
function FormatDay(d , format){
while(format.indexOf("d") > -1){
var regex = /[d] /;
format = format.replace(regex,function(w) {
switch(w.length){
case 0:break;
case 1:
return d.getDate();
case 2:
return d.getDate() < 10 ? "0" d.getDate() : d.getDate();
case 3:
switch(d.getDay()){
case 0:
return "Day" ;
case 1:
return "一";
case 2:
return "二";
case 3:
return "三";
case 4:
return "四";
case 5:
return "五";
case 6:
return "六";
}
default:
switch(d .getDay()){
case 0:
return "Sunday";
case 1:
return "Monday";
case 2:
return "Tuesday";
case 3:
return "Wednesday";
case 4:
return "Thursday";
case 5:
return "Friday";
case 6:
return "Saturday";
}
}
});
}
return format;
}
//Format hour
//H: 24 hours System
//h: 12-hour format
function FormatHour(d, format){
while(format.indexOf("H") > -1){
var regex = /[H ] /;
format = format.replace(regex,function(w){
switch(w.length){
case 0:break;
case 1:
return d.getHours ();
default:
return d.getHours() < 10 ? "0" d.getHours() : d.getHours();
}
});
}
while(format.indexOf("h") > -1){
var regex = /[h] /;
format = format.replace(regex,function(w){
switch(w.length){
case 0:break;
case 1:
return d.getHours() > 12 ? d.getHours() - 12 : d.getHours();
default:
var t = d.getHours() > 12 ? d.getHours() - 12 : d.getHours();
return t < 10 ? "0" t : t;
}
});
}
return format;
}
//Format minutes
function FormatMinute(d, format){
while(format.indexOf( "m") > -1){
var regex = /[m] /;
format = format.replace(regex,function(w){
switch(w.length){
case 0:break;
case 1:
return d.getMinutes();
default:
return d.getMinutes() < 10 ? "0" d.getMinutes() : d .getMinutes();
}
});
}
return format;
}
//Format seconds
function FormatSecond(d, format){
while(format.indexOf("s") > -1){
var regex = /[s] /;
format = format.replace(regex,function(w){
switch( w.length){
case 0:break;
case 1:
return d.getSeconds();
default:
return d.getSeconds() < 10 ? "0" d.getSeconds() : d.getSeconds();
}
});
}
return format;
}

Resources used in this article
DateExtension.js download
W3C School browsing
Browse for more support about Date objects
Date operation class DateTime function code implemented by js

pdf version download address