函数不从ajax调用返回消息

Question

I want my function, which does an ajax call to controller, to return message from response.

I've tried this, but it doesnt work. How can acchieve my goal? is there a better solution for this?

var exists = personExists ();

   if (exists != null) {
      alert('The person already exists');
      return;
   }

var personExists = function () {

   var exists = false;
   var errorMsg = null;

$.ajax({
      url: "@Url.Action("PersonExist", "Person")",
      type: "POST",
      dataType: 'json',
      data: { name: self.name(), socialSecurityNumber: self.socialSecurityNumber() },
      async: false,
      contentType: "application/json",
      success: function (response) {
          if (response.exists) {
             exists = true;
             errorMsg = response.message;
          }
      }
 });

 if (exists)
   return errorMsg;

 return null;
};

Answer 1

You need to use a callback:

function getErrorMessage(message) {
    //do whatever
}

Inside the AJAX request:

$.ajax({
  url: "@Url.Action("PersonExist", "Person")",
  type: "POST",
  dataType: 'json',
  data: { name: self.name(), socialSecurityNumber: self.socialSecurityNumber() },
  async: false,
  contentType: "application/json",
  success: function (response) {
      if (response.exists) {
         exists = true;
         getErrorMessage(response.message); //callback
      }
  }

});

Answer 2

You can do that with callback functions;

var personExists = function (callback) {

   var exists = false;
   var errorMsg = null;

    $.ajax({
          url: "@Url.Action("PersonExist", "Person")",
          type: "POST",
          dataType: 'json',
          data: { name: self.name(), socialSecurityNumber: self.socialSecurityNumber() },
          async: false,
          contentType: "application/json",
          success: function (response) {
              if (response.exists) {
                 exists = true;
                 errorMsg = response.message;
                 callback(exists, errorMsg);
              }
          }
     });

     if (exists)
       return errorMsg;

     return null;
};

And usage;

personExists(function(exists, err) {
    if (exists != null) {
      alert('The person already exists');
      return;
   }    
});

Simply, you can pass exists and errorMsg to callback. See here for further detail on callback functions