Thinking about the formatting of data text in JavaScript

In some scenarios where accuracy is not as accurate as possible, we can directly Number.prototype.toFixed() implement the need to retain two decimal places.

var num = 123.45678console.log(num.toFixed(2)) //123.46var num2 = 12console.log(num2.toFixed(2)) //12.00

However, if it happens that the number is an integer, then 12.00 the format is output, and we often require that the integer be 00 output directly for the integer that follows. So write it that way.

var num=123.45678console. Log (num.tofixed (2).  //123.46var num2 = 12console. Log (num2. ToFixed (2).  Replace ( //12            

toFixed() replace() Replace the string that appears immediately after the integer .00 .

PS: Number.prototype.toFixed The return is a string

The number is [0-9] in the case of the pre-complement 0

In the case of outputting some numbers, if it is less than ten , you need to fill in the front 0, especially when the output date time.

Before using the Date object to obtain the relevant time data to determine whether it is less than ten, if it is to fill 0.

var date = new Date()var min = date.getMinutes()min = min < 10 ? ‘0‘ + min : minconsole.log(min) //08

Later I felt that it was not elegant enough, and the code was so numerous that I thought of replacing it with strings.

var date = new Date()var min = String(date.getMinutes()).replace(/^(\d{1})$/, ‘0$1‘)console.log(min) //08

This makes use of regular to match to single-digit case directly in front plus 0 , a line of code, more elegant.

To continue with the derivation, I basically have to do in the date format when the number needs to be replaced, why not directly replace the entire string? For example, it will be 2017-1-8 12:8 replaced 2017-01-08 12:08 .

var date = ‘2017-1-8 12:8‘.replace(/\b\d{1}\b/g, ‘0$&‘)console.log(date)

The entire string substitution is done through regular, no longer targeted to some parts of the processing. Finally, a complete example of the formatted date function is given.

function FormatDate(Source,Format= ' Yyyy-mm-dd '){Let date=NewDate ();if (typeof Source===' String ') format= Source;if (typeof Source===' Number ') date=NewDate (source);if (typeof Source===' Object ') date= Source;Const year=Date.getFullYear ();Const MONTH=Date.GetMonth ()+1;Const DAY=Date.GetDate ();Const HOUR=Date.GetHours ();Const Miniute=Date.Getminutes ();Const second=Date.Getseconds ();ReturnFormat.Replace ' yyyy '  Replace ( ' MM ' , month).  Replace ( ' DD '  Replace ( ' hh '  Replace ( ' mm '  Replace ( ' SS '  Replace (/\b\d{1}\b/g< Span class= "hljs-string" > ' 0$& ') ;}         

Thinking about formatting data text in JavaScript