Javascript函数AJAX调用返回undefined

Question

当进行AJAX调用时，onsuccess不会返回字符串构建器数据，而是返回undefined。

var MyApp = window.MyApp || {}; 

MyApp.Data = function() { 
    var temp = 'Test', 
    ShowMethod = function() { 
     $.ajax({ 
      url: "some url", 
      type: "GET", 
      headers: { 
       "accept": "application/json; odata=verbose" 
      }, 
      success: ShowMethodSucceeded, 
      error: FailedMethod 
     }); 
    }, 
    ShowMethodSucceeded = function(data) { 
     var results = data.d.results; 
     if(results.length > 0) { 
      temp = ''; 
      for(var i = 0; i < results.length; i++) { 
       temp += 'string builder stuff'; 
      } 
     } else { 
      alert('no records'); 
     } 
     return temp; 
    }, 
    FailedMethod = function() { 
     alert('error'); 
    }; 
    return { 
     Show: ShowMethod 
    }; 
}(); 

$(document).ready(function() { 
    $('#divResults').append(MyApp.Data.Show()); 
}); 

此外，这里有几个不同版本的代码不会收获正确的结果。

MyApp.Data = function() { 
    var temp = 'Test', 
    ShowMethod = function() { 
     $.ajax({ 
      url: "some url", 
      type: "GET", 
      headers: { 
       "accept": "application/json; odata=verbose" 
      }, 
      success: ShowMethodSucceeded, 
      error: FailedMethod 
     }); 
    }, 
    return temp; 
    // returns 'Test' instead of the string builder 

MyApp.Data = function() { 
    var temp = 'Test', 
    ShowMethod = function() { 
     $.ajax({ 
      url: "some url", 
      type: "GET", 
      headers: { 
       "accept": "application/json; odata=verbose" 
      }, 
      success: function(data) { temp = data; }, 
      error: FailedMethod 
     }); 
    }, 
    return temp; 
    // returns 'Test' instead of the JSON from data 

如何从AJAX调用的成功函数中返回数据？

在进行AJAX调用时，函数完成执行并且返回变量尚未填充。 UI是动态构建的，我想使用字符串构建器函数来返回字符串以附加动态构建UI的函数。

预先感谢您。

Answer 1

我想你会需要在整个下探回调，像这样：

MyApp.Data = function() { 
    var temp = 'Test', 
    ShowMethod = function(cb) { // added cb 
     $.ajax({ 
      url: "some url", 
      type: "GET", 
      headers: { 
       "accept": "application/json; odata=verbose" 
      }, 
      success: function (data) { 
       ShowMethodSucceeded(data, cb); // pass cb through 
      }, 
      error: FailedMethod 
     }); 
    }, 
    ShowMethodSucceeded = function(data, cb) { // added cb 
     var results = data.d.results; 
     if(results.length > 0) { 
      temp = ''; 
      for(var i = 0; i < results.length; i++) { 
       temp += 'string builder stuff'; 
      } 
     } else { 
      alert('no records'); 
     } 
     cb(temp); // call cb with the result 
    }, 
    FailedMethod = function() { 
     alert('error'); 
    }; 
    return { 
     Show: ShowMethod 
    }; 
}(); 

$(document).ready(function() { 
    MyApp.Data.Show(function (result) { // pass a callback 
     $('#divResults').append(result); // use the result 
    }); 
});