var url = 'http://localhost/dld/index.php/welcome/index?attrs=1,黑色;2,大号;3,侧滑;';
var replacement = '1,绿色;';
alert(url.replace(new RegExp(/^\d+/gi.exec(replacement)+',[^,;]+;','gi'),replacement));
var replacement = '2,小号;';
alert(url.replace(new RegExp(/^\d+/gi.exec(replacement)+',[^,;]+;','gi'),replacement));
var replacement = '1,绿色;';
alert(url.replace(new RegExp(/^\d+/gi.exec(replacement)+',[^,;]+;','gi'),replacement));
var replacement = '2,小号;';
alert(url.replace(new RegExp(/^\d+/gi.exec(replacement)+',[^,;]+;','gi'),replacement));
var replacement = '1,绿色;';
alert(url.replace(new RegExp(/^\d+/gi.exec(replacement)+',[^,;]+;','gi'),'') + replacement);
var replacement = '2,小号;';
alert(url.replace(new RegExp(/^\d+/gi.exec(replacement)+',[^,;]+;','gi'),'') + replacement);
r = '2,小号;';
e = eval('/' + r.match(/\d+,/) + '.+?;/');
s = s.replace(e, r);r = '1,绿色;';
e = eval('/' + r.match(/\d+,/) + '.+?;/');
s = s.replace(e, r);
alert(s);