The regular limit is entered as a number, and a new notation of up to 2 decimal places is entered

Originally the small program needs a limit text box input as a number, and retain the effect of up to 2 decimal places, the example found on the internet feel a bit cumbersome, wrote a.

The code is simple, and is mainly handled by the regular group matching feature:

// Check input text, limit only to numbers and numbers with up to 2 decimal places  function (text) {    var reg =/^ (\.*) (\d+) (\.?) (\d{0,2}). *$/g;     if // regular Match Pass, extract valid text      Text = Text.replace (reg, ' $2$3$4 ');    }     Else // regular match does not pass, empty directly      Text = ';    }     return // returns the text that meets the requirements (numeric and with a maximum of 2 decimal places)  }

1, the example used in the Small program demo:

*.wxml File Code:

<view class= ' Row ' >        <view class= ' title ' > Text input limit input numbers with a maximum of 2 decimal places </view>        <input type= ' Digit ' placeholder= ' Please enter a valid number ' bindinput= ' inputnum ' class= ' numinput '/>    </view>

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Corresponding *.js file key code:

//listening for text inputInputnum:function(e) {return  This. Checkinputtext (E.detail.value); },  //Check input text, limit only to numbers and numbers with up to 2 decimal placesCheckinputtext:function(text) {varReg =/^ (\.*) (\d+) (\.?) (\d{0,2}). *$/G; if(Reg.test (text)) {//regular Match Pass, extract valid textText = Text.replace (reg, ' $2$3$4 '); }    Else{//regular match does not pass, empty directlyText = ' '; }    returnText//returns the text that meets the requirements (numeric and with a maximum of 2 decimal places)}

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2. Use the sample demo on the Web page:

<div> <br/> //Listen for text box input, limit its input to a number, and enter up to 2 decimal places only            functionInputtext (obj) {obj.value=Checkinputtext (Obj.value); }            //Check input text, limit only to numbers and numbers with up to 2 decimal places            functionCheckinputtext (text) {varReg =/^ (\.*) (\d+) (\.?) (\d{0,2}). *$/G; if(Reg.test (text)) {//regular Match Pass, extract valid textText = Text.replace (reg, ' $2$3$4 '); }                Else{//regular match does not pass, empty directlyText = ' '; }                returntext; }        </script>

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3, String.prototype.replace () use

The Replace method of a string object can replace a matching value. It accepts two parameters,

The first parameter is the content to be replaced, can be expressed as a string, or a regular expression can be used to represent the search pattern;

The second parameter is the content that represents the first parameter to replace.

When using a regular expression, the second parameter of the Replace method can use the dollar sign $, which is used to refer to the substituted content:

$&: Matched substring $: matches the preceding text $': matches theresult of the text $n: matches the successful nth set of Contents, n is the natural number starting from 1 $$: The dollar sign $

Examples of how to use it:

//1, the matching Group interchange locationvarstr1 = ' Hello World '. Replace (/(\w+) \s (\w+)/, ' $ $ $ '); Console.log (' str1 = ' +str1); //str1 = World Hello//2. Overwrite the matching valuesvarSTR2 = ' abc '. replace (' B ', ' [$ '-$&-$\ '] '); Console.log (' str2 = ' +str2); //str2 = a[a-b-C]c//3. The second parameter of the Replace method can also be a function that replaces each match with a function return valuevarSTR3 = ' 3 and 5 '. Replace (/[0-9]+/g,function(match) {return2 *match;}); Console.log (' STR3 = ' +STR3); //STR3 = 6 and ten//4, replace the substitution method The second parameter of the replacement function, you can also accept multiple parameters. //The first parameter is the captured content, and the parameter after the second parameter represents the group match (how many groups match, how many corresponding parameters are matched)//Below is a sample page template replacementvarPrices = {  ' P1 ': ' ￥1.99 ',  ' P2 ': ' ￥9.99 ',  ' P3 ': ' ￥5.00 '};varTemplate = ' <span id= ' p1 ' ></span> ' + ' <span id= ' p2 ' ></span> ' + ' <span id= ' p3 ' &GT;&LT;/SPAN&G t; ';varSTR4 =Template.replace (/(<span id= ") (. *?) (">) (<\/span>)/G,function(Match, $, $, $ $, $4){    return$ + $ + $ + prices[$2] + $4; }); Console.log (' STR4 = ' +STR4);//STR4 = <span id= "P1" >￥1.99</span><span id= "P2" >￥9.99</span><span id= "P3" >￥5.00 </span>

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Then you should understand the regular/^ (\.*) (\d+) (\.?) (\d{0,2}). *$/g means a total of 4 matching groups

var reg =/^ (\.*) (\d+) (\.?) (\d{0,2}). *$/G; /* The Regular expression reg contains 4 matching groups: (\.*): The first character that matches the input is a decimal point. The corresponding group match symbol $ (\d+): matches the input decimal points. The previous number, corresponding to the group match symbol, $ (\.?): Matches the decimal point, the corresponding group matches the symbol $ d{0,2}): matches the number after the decimal point, after the decimal limit several decimal repeat symbol {M,n} can be written to a few, corresponding group matching symbol $4* /

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