等待AJAX​​请求，然后完成jQuery

I have a piece of jQuery code:

var newData = checkCP(somedata);
if(newData=="hi"){
    alert("Welcom");
}

 function checkCP(jsData){

    $.ajax({
        type: "POST",
        url: "Process.php",
        data: jsData,
        dataType: "json",
        success: function(data){
            if(data.match==1)
                return "hi";    
            else
                return "bye";
        }
    });
}

I don't know why the welcome alert never shows up. I checked everything; the PHP file returns 1, but apparently before it waits on the AJAX response it passes the

if(new=="hi"){
    alert("Welcom");
}

Is there any way to wait for the AJAX response, then read the rest of codes in jQuery?

Yes, you can set the 'async' option in $.ajax() to false.

$.ajax({
            type: "POST",
            async: false,
            url: "Process.php",
            data: jsData,
            dataType: "json",
            success: function(data){
                if(data.match==1)
              return "hi";  
            else
              return "bye";
            }

Firstly, please don't use 'new' as a variable name. 'new' already means something.

Now onto the actual question...

when you call checkCP jquery does the ajax post successfully and automatically waits for a response before execuiting the success function. the thing is that the success function is a stand-alone function and returning a value from that does not return anything from checkCP. checkCP is returning null.

As proof try sticking an alert in your success function.

Something like this should do the trick:

function deal_with_checkCP_result(result)
{
     if(result=="hi"){
     alert("Welcom");
    }
}

function checkCP(jsData,callback){

        $.ajax({
            type: "POST",
            url: "Process.php",
            data: jsData,
            dataType: "json",
            success: function(data){
                if(data.match==1)
              callback( "hi");  
            else
              callback( "bye");
            }
      });

    }

Pass deal_with_checkCP_result as callback