jQuery：所有嵌套的ajax调用也都完成后，调用then函数

如何解决jQuery：所有嵌套的ajax调用也都完成后，调用then函数

我正在尝试借助function和when编写一些嵌套的ajax调用。但是目前，我的then函数无法正常工作。我想在完成所有Ajax调用（包括嵌套调用）时调用then函数。我想在以下时间调用功能

this.getDescendants(resourceId[1],resourceData.limit+resourceData.offset); 

对于所有主要的ajax调用，

也已完成。当前，然后在嵌套ajax调用完成之前完成。

    getUserInfo: function(){
        $.ajax({
            type: "GET",contentType: "application/json",url: UserURL,context: this,beforeSend: function (xhr) {
              $('#fade-wrapper').fadeIn();
              xhr.setRequestHeader('Authorization',"Basic "+this._basicCred);
            },success: function(resourceData) {
                if(resourceData.resources != undefined && resourceData.resources.length > 0){
                    var deferreds = [];
                    for (var i=0; i < resourceData.resources.length; ++i){
                      var deferred = this.getDescendants(resourceData.resources[i],0);
                      deferreds.push(deferred);
                    }
                    $.when.apply($,deferreds).then(function() {
                        var currentContext = this[0];
                        console.log(currentContext);
                        console.log("Then called.");
                    });
                } else {
                    alert("No visible resource has been found.");
                }
            }.bind(this),error: function(xhr,status,err) {
                console.error( status,err.toString());
                $('#fade-wrapper').fadeOut();
                alert("Error has occurred,please contact administrator in case the problem persists.");
                return null;
            }.bind(this)
        });
        
    },getDescendants: function(resId,offset){
        return $.ajax({
            type: "GET",data: {"resId":resId},url: DesedentURL+"?limit=10&offset="+offset,beforeSend: function (xhr) {
                xhr.setRequestHeader('Authorization',success: function(resourceData,textStatus,xhr) {
                if(this._resResults == undefined){
                    this._resResults = [];
                }
                this._resResults.push(resourceData);
                console.log("resourceData");
                console.log(resourceData);
                if(resourceData.totalResults > (resourceData.limit+resourceData.offset) ){
                    var resourceId = resourceData.links[0].href.match("resources/(.*)/descendants");
                    console.log(resourceId);
                    this.getDescendants(resourceId[1],resourceData.limit+resourceData.offset);
                }
            }.bind(this),please contact administrator in case the problem persists.");
                return null;
            }.bind(this)
        });
    }