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在一系列异步XHR调用之后添加“回调”的最佳方法

asynchronous ajax jquery javascript

SBUJOLD · 技术社区 · 16 年前

$(search).each(function() {
 $.ajax({
  url: 'save.x3?id='+$(this).attr("id")+'value='$(this).data("value");
  success: function(o){
   //Update UI
  },
  error: function(o){
   //Update UI
  }
 });
});

//code to do after saving...

显然,“保存后要执行的代码…”通常在所有请求完成之前执行。在理想情况下,我希望服务器端代码一次处理所有请求,并在保存成功回调后移动//代码,但假设这不可能,我将代码更改为类似这样的代码,以确保在继续之前返回所有请求,我仍然不喜欢这些请求:

var recs = [];
$(search).each(function() {
 recs[recs.length] = 'save.x3?id='+$(this).attr("id")+'value='$(this).data("value");
});

var counter = 0;
function saveRecords(){
 $.ajax({
  url: recs[counter],
  success: function(o){
   //Update progress
   if (counter<recs.length){
    counter++;
    saveRecords();
   }else{
    doneSavingRecords();
   }
  },
  error: function(o){
   //Update progress
   doneSavingRecords(o.status);
  }
 });
}

function doneSavingRecords(text){
 //code to do after saving...
}

if (recs.length>0){
 saveRecords();  //will recursively callback itself until a failed request or until all records were saved
}else{
 doneSavingRecords();
}

因此,我正在寻找一种“最佳”方法,向一系列异步调用添加一点同步功能?

谢谢

4 回复 | 直到 16 年前

Doug Neiner 16 年前

更好的答案 :

function saveRecords(callback, errorCallback){
  $('<div></div>').ajaxStop(function(){
    $(this).remove(); // Keep future AJAX events from effecting this
    callback();
  }).ajaxError(function(e, xhr, options, err){
    errorCallback(e, xhr, options, err);
  });

  $(search).each(function() {
    $.get('save.x3', { id: $(this).attr("id"), value: $(this).data("value") });
  });
}

saveRecords(function(){
   // Complete will fire after all requests have completed with a success or error
}, function(e, xhr, options, err){
   // Error will fire for every error
});

原始答案 :如果它们需要按特定顺序排列,或者页面上有其他常规AJAX事件会影响 ajaxStop ,但速度会慢一些:

function saveRecords(callback){
  var recs = $(search).map(function(i, obj) {
   return { id: $(obj).attr("id"), value: $(obj).data("value") };
  });

  var save = function(){
   if(!recs.length) return callback();

   $.ajax({
    url: 'save.x3',
    data: recs.shift(), // shift removes/returns the first item in an array
    success: function(o){
     save();
    },
    error: function(o){
     //Update progress
     callback(o.status);
    }
   });
  }

  save();
}

然后你可以这样称呼它:

saveRecords(function(error){
   // This function will run on error or after all 
   // commands have run
});

Drew Wills 16 年前

$.ajaxStop() 为此目的。

Aaron Martins 13 年前

    //a list of URLs for which we'll make async requests
    var queue = ['/something.json', '/another.json']; 

    //will contain our return data so we can work with it
    //in our final unified callback ('displayAll' in this example)
    var data = [];

    //work through the queue, dispatch requests, check if complete
    function processQueue( queue ){
        for(var i = 0; i < queue.length; i++){
            $.getJSON( queue[i], function( returnData ) {
                data.push(returnData);

                //reduce the length of queue by 1
                //don't care what URL is discarded, only that length is -1
                queue.pop();

                checkIfLast(displayAll(data));
            }).fail(function() {
                throw new Error("Unable to fetch resource: " + queue[i]);
            });
        }
    }

    //see if this is last successful AJAX (when queue == 0 it is last)
    //if this is the last success, run the callback
    //otherwise don't do anything
    function checkIfLast(callback){
        if(queue.length == 0){
            callback();
        }
    }

    //when all the things are done
    function displayAll(things){
        console.log(things); //show all data after final ajax request has completed.
    }

    //begin
    processQueue();

编辑:我应该补充一点,我专门针对队列中任意数量的项目。您可以简单地添加另一个URL,这将同样有效。

Geoff Moller 16 年前

Closure的net.BulkLoader(或类似的方法)将为您提供:

见: goog.net.BulkLoader.prototype.handleSuccess(用于单独调用) goog.net.BulkLoader.prototype.finishLoad(用于完成所有调用)