var user='xia&&min**';
user=user.replace(/[^A-Za-z\d_-]+/,'');   //需要再次赋值
console.log(user); //xiamin**
user = user.replace(/[^A-Za-z\d_-]+/g, '');  //全局进行替换
console.log(user); //xiamin

var email='nettuts@tutsplus.com';
var result=email.replace(/([A-Za-z_\d-]+)@([A-Za-z_\d-]+)\.[a-z]{2,4}/ig,'$1,$2');
console.log(result); //nettuts tutsplus

var name='xiamin';
var result=/[A-Za-z-_]+/.test(name);
console.log(result);

var name='xiamin';
var result=name.match(/i/g);
console.log(result); //(2) ["i", "i"]

var url ='http://localhost:8080?name=xiamin';
var result=url.match(/^(.+)\?(.+)/i);
console.log(result);//"http://localhost:8080?name=xiamin?" "http://localhost:8080" "name=xiamin"

var url ='http://localhost:8080?name=xiamin#dnsjdnw';
var result=url.match(/#(.+)/i);
console.log(result);//"#dnsjdnw", "dnsjdnw"

var url ='http://localhost:8080?name=xiamin#dnsjdnw';
var result=url.match(/(ht|f)tps?:/i);
console.log(result);//"http:", "ht"

var url ='http://www.baidu.com';
var result=url.match(/.+\.[a-z]{2,4}/ig);
console.log(result);//[url=http://www.baidu.com]http://www.baidu.com[/url]