限界正規表現

to_link.js

function to_link(str) {
    var r_alpha = '[A-Za-z]';
    var r_escape = '(?:%[0-9A-Fa-f]{2})';
    var r_xalpha = '(?:[-0-9A-Za-z$_@.&!*"\'(),]|'+r_escape+')';
    var r_xpalpha = '(?:\\+|'+r_xalpha+')';
    var r_xealpha = '(?:=|'+r_xalpha+')';
    var r_hostname = '(?:'+r_alpha+r_xpalpha+')(?:\\.'+r_alpha+r_xpalpha+')*';
    var r_hostnumber = '(?:[0-9]+\\.[0-9]+\\.[0-9]+\\.[0-9]+)';
    var r_host = '(?:'+r_hostname+'|'+r_hostnumber+')';
    var r_port = '(?::[0-9]+)'
    var r_path = '(?:'+r_xpalpha+'+)(?:\\/'+r_xpalpha+'*)*';
    var r_search = '(?:'+r_xealpha+'+)(?:\\+(?:'+r_xealpha+'+))*'
    var r_httpaddress = 'https?:\\/\\/'+r_host+r_port+'?'+'\\/?(?:'+r_path+')*'+'(?:\\?'+r_search+')?'+'(?:#'+r_xpalpha+'+)?';

    // console.log(r_httpaddress);

    return (str+'').replace(new RegExp(r_httpaddress, 'g'), '<a href="$&" target="_blank">$&</a>');
}