JavaScript'函数调用'事件监听器

Question

function addAndRemove() {
    if (mapData.initialZoom && !cameraStatus.locked) {
        cameraStatus.locked = true;
        var ajaxRequest = null;


        var abortMission = setTimeout(function () {

            /* Here is where I need the event listener.
             * If the function is called again then we need to
             * cancel our existing ajax request */

            if (ajaxRequest) {
                ajaxRequest.abort();
                updatePrompt({text: "Cancelled ajax"});
            }

            cameraStatus.locked = false;
        }, 1000);
    }
}

正如我在代码中的评论中所述，我需要能够在执行过程中听取是否再次调用addAndRemove。我只想取消现有的Ajax请求，如果请求了新的Ajax请求。我怎么能这样做？

Answer 1

您需要使用闭包在函数中创建状态。

你可以用这种方式重构你的功能。

var addAndRemove = (function(){
  var ajaxRequest = null; // --> move ajaxRequest variable here
  return function () {
    if (mapData.initialZoom && !cameraStatus.locked) {
        cameraStatus.locked = true;

        var abortMission = setTimeout(function () {

            /* Here is where I need the event listener.
             * If the function is called again then we need to
             * cancel our existing ajax request */

            if (ajaxRequest) {
                ajaxRequest.abort();
                updatePrompt({text: "Cancelled ajax"});
            }

            cameraStatus.locked = false;
        }, 1000);
    }
  }
}());

无论调用函数的时间长短，ajaxRequest都将指向相同的引用。