登錄密碼，眼睛效果，點擊顯示，點擊隱藏

$(document).ready(function(){
    $(".userinfo_main_csrq i").click(function(){

        if ($( this ).siblings("input").attr("type") == "text") {
            $( this ).siblings("input")[0].type = "password";  
            $( this ).removeClass("userinfo_main_csrq_i");   
        }else{
            $( this ).siblings("input")[0].type = "text"; 
            $( this ).addClass("userinfo_main_csrq_i");   
        }   
    });
});

<div class="userinfo_main_csrq"><span>原密碼</span><b>|</b><input name="old_password" type="password" maxlength="25"><i></i></div>