JavaScript positive expression Reverse Reference example Introduction

This article mainly introduces the JavaScript in the regular expression of the reverse reference, the need for friends can refer to the

Recently encountered a requirement, pass in a string, insert a space example every three characters: incoming abcd1234 output ABC D12 34 think about it, prepare to write a function The following code is as follows: function Appendspace (s) {V  Ar length = s.length;  var result = "";  var last = 0;  for (var i = 3;i<=length;i=i+3,last = last+3) {result = Result+s.substring (i-3,i) + "";  result = Result+s.substring (last,length);  return result;    Feel this function is a bit of a dick ... Then replace () the regular expression substitution method code is as follows:/* *$1 represents the first pair of parentheses in a reference matching rule (here is "(. { 3}) "The text that is hit will be output directly without parenthesis */function Insertspace (s) {var result =s.replace (/. {  3})/g, "$";  return result; }