异步错误冻结网站

My website always freze with async false. I need to wait confirmation for execute script.

$.ajax({
    type: "POST",
    url: url,
    data: form.serialize(),
    async: false,
    success: function(data) {
        var conf = data;
    }
});

if(conf == "ok")
{
   alert('ok');
}

What is the good model for use this with async true please? I have tested with return but not work.

Edit:

 $(function(){
        window.wheel = {

            init: {},

            wheelof: function() { 
    $.ajax({
        type: "POST",
        url: url,
        data: form.serialize(),
        async: true,
        success: function(data) {
            alert('ok');
        }
    });
 }
 }

        window.wheel.init();
});

$.ajax({
    type: "POST",
    url: url,
    data: form.serialize(),
    async: true,
    success: function(data) {
        var conf = data;
        check(conf);      
    }
});

Pass data values to separate function after success.

function check(conf){
if(conf == "ok")
 {
   alert('ok');
 }
}

$.ajax({
    type: "POST",
    url: url,
    data: form.serialize(),
    async: true,
    success: function(data) {
        var conf = data;
        if ( conf === "ok" ) {
           alert( "ok" )        
        }    
    }
});

Old question but didn't see any good answer, so here is mine from my experience:

$.ajax({
    type: 'post',
    url: url,
    data: form.serialize()
})
.done(function(data){
    var conf = data;
    check(conf);
});

function check(conf){
    if(conf == "ok"){
        alert('ok');
    }
}

This way the user experience doesn't suffer from unresponsive webpage. Using asynnc: false is not a good solution.