'use strict';
var checkRegisterForm = function () {
var
    usr = document.querySelector('#username'),
    pwd = document.querySelector('#password'),
    pwd_2 = document.querySelector('#password-2'),
    usr_re = /^\w{3,10}/,
    pwd_re = /.{6,20}/;

if (!usr_re.test(usr.value)) {
    alert('用户名必须是3-10位的数字或英文字母');
    return false;
} else if (!pwd_re.test(pwd.value)) {
    alert('密码必须是6-20位');
    return false;
} else if (pwd.value !== pwd_2.value) {
    alert('两次密码不一致');
    return false;
} 
return true;
}