JS中关于正则的巧妙操作

var msg="dsada[emoji:37]dsadas[emoji:3900]法拉綏芬河";
function fetch(msg) {
 var match, result = msg,
 reg = /\[emoji:\d+\]/g,
 emojiIndex,
 totalEmojiNum = 45;
 while (match = reg.exec(msg)) {
 console.log(match[0]);//[emoji:37],[emoji:3900]
 emojiIndex = match[0].slice(7, -1);
 console.log(emojiIndex);//37,3900
 if (emojiIndex > totalEmojiNum) {
 result = result.replace(match[0], '[X]');
 } else {
 result = result.replace(match[0], '<img src="images/eomji_' + emojiIndex + '.gif" />');
 };
 };
 return result;//"dsada<img src="images/eomji_37.gif" />dsadas[X]法拉綏芬河"
}
fetch(msg);