Unable to replace using RegExp

Question

I am trying to replace a particular set of strings using RegExp but it is not replacing. The regex I am trying is

\@223(?:\D|'')\gm

The set of strings to test on are these

@223 ->Replace 223 with #
@223+@33 ->Replace 223 with #
@22;    ->Not Replace
@2234   ->Not Replace 
@22234  ->Not Replace
@223@44  ->Replace 223 with #

Answer 1

if this what you went :

var string = `
@223
@223+@33
@22;
@2234
@22234
@223@44
`;
regex = /(?<=@)(223)(?=\D)/g;
string = string.replace(regex, "#");
console.log(string);

output :

@#
@#+@33
@22;
@2234
@22234
@#@44

explanation :

(?<=@) : test if leaded by @ character.
(?=\D) : followed by any character except digit