JavaScript matches the character of the even position of the string and matches the $ symbol

A string that is known to be #####, now needs to replace the # of the even position with &.

function Replacedemo () {      var s = "1#2#3#4#5#";       var regex =/#/g;       var index = 1;      S=s.replace (regex,function() {index++;  Return index%2? ' & ': Arguments[0]});       return s;  }  

Comments:

1. Because the entire string needs to be matched, the policy expression needs to add the G parameter.

2.index is used to record the position of a character matched to a regular expression to find the character of an even position.

3.arguments is an internal object? Arguments[0] is the match to the character value, where #;arguments[1] is the match to the character value at the position of the original string.

A string of $$$$$ is known, and it is now necessary to replace the $ & for even position.

function Replacedemo () {      var s = "$$$$$";       var // /$/g;      var index = 1;      S=s.replace (regex,function() {index++;  Return index%2? ' & ': Arguments[0]});       return s;  }  

Comments:

1. Special symbol $ in regular expressions The meaning of the match string end position. Need to escape by//symbol when matching

JavaScript matches the character of the even position of the string and matches the $ symbol