使用Ajax承诺/推迟

Question

I am trying to get an Ajax promise using the code below. Because my function makes another ajax call before initiating the actual one , for getting the authKey , The promise (that should have been returned) from the actual call is null, & I cannot use .then() on it because I think I am not getting anything in return from it. I am not sure why.

What am I doing wrong here? Is there any other way to go about this. I call getAjaxPromise() like mentioned below but get null in return:

  getAjaxPromise(myUrl, true, myType, myContentType, mySuccessFunction, myFailureFunction, myData, true) .then(function(data) //.then() gives undefined-null error { //Do something with the data returned form actual Ajax call. }); 

 self.getAjaxPromise = function(url, async, type, contentType, successCallback, errorCallback, data, isSecureCall) { if (isSecureCall) { var tokenPromise = getTokenPromiseFromServer(); //Another Ajax call to get latest token from service tokenPromise.then(function(tokenData) { //This then runs fine return $.ajax({ beforeSend: function(request) { request.setRequestHeader("authKey", tokenData.key); }, url: url, async: async, type: type, contentType: contentType, success: successCallback, //Success callback runs fine, then() does not error: errorCallback, //Error callback runs fine, then() does not data: JSON.stringify(data) }); }); } else { //Just one ajax call return $.ajax({ beforeSend: function(request) { request.setRequestHeader("authKey", "anonymous"); }, url: url, async: async, type: type, contentType: contentType, success: successCallback, error: errorCallback, data: JSON.stringify(data) }); }); } }; 

Answer 1

you forgot to return the getTokenPromiseFromServer
if isSecureCall is true your function return null

 self.getAjaxPromise = function(url, async, type, contentType, successCallback, errorCallback, data, isSecureCall) { if (isSecureCall) { return getTokenPromiseFromServer().then(function(tokenData) { return $.ajax({ beforeSend: function(request) { request.setRequestHeader("authKey", tokenData.key); }, url: url, async: async, type: type, contentType: contentType, success: successCallback, //Success callback runs fine, then() does not error: errorCallback, //Error callback runs fine, then() does not data: JSON.stringify(data) }); }); } else { //Just one ajax call return $.ajax({ beforeSend: function(request) { request.setRequestHeader("authKey", "anonymous"); }, url: url, async: async, type: type, contentType: contentType, success: successCallback, error: errorCallback, data: JSON.stringify(data) }); }); } }; 

Answer 2

You had forgot to return the promise inside the if statement, you are return it only on else, the fixed code below:

 self.getAjaxPromise = function(url, async, type, contentType, successCallback, errorCallback, data, isSecureCall) { if (isSecureCall) { var tokenPromise = getTokenPromiseFromServer(); //Another Ajax call to get latest token from service tokenPromise.then(function(tokenData) { return $.ajax({ beforeSend: function(request) { request.setRequestHeader("authKey", tokenData.key); }, url: url, async: async, type: type, contentType: contentType, success: successCallback, //Success callback runs fine, then() does not error: errorCallback, //Error callback runs fine, then() does not data: JSON.stringify(data) }); }); return tokenPromise; } else { //Just one ajax call return $.ajax({ beforeSend: function(request) { request.setRequestHeader("authKey", "anonymous"); }, url: url, async: async, type: type, contentType: contentType, success: successCallback, error: errorCallback, data: JSON.stringify(data) }); }); } }; 

Answer 3

You forgot to return tokenPromise you must return it from first if

if (isSecureCall) {
    var tokenPromise = getTokenPromiseFromServer(); //Another Ajax call to get latest token from service

    // ...

    return tokenPromise;
  }