浏览器成功接收到给定的MVC Web API响应-如何确保在服务器端

Question

我正在为GET方法编写web API。此方法将返回JSON对象作为响应。我需要一个动作过滤器方法或一个事件，当浏览器成功接收到响应时自动调用。

Answer 1

以下内容改编自Nicholas Zakas的Professional JavaScript for Web Developers (3rd Edition):

Ajax功能:

function Ajax() {
    var xhr, responseObj, getCompletionFunction;
    var completionFunction;
    this.setGetCompletionFunction = function (value) { getCompletionFunction = value; }
    this.getRequest = function (url) {
        completionFunction = getCompletionFunction;
        xhr = new XMLHttpRequest();
        xhr.onreadystatechange = readyStateChangeFunction;
        xhr.open("get", url, true);
        xhr.setRequestHeader("Content-Type", "application/json");
        xhr.send(null);
    }
    function readyStateChangeFunction() {
        if (xhr.readyState == 4) {
            if (xhr.status >= 200 && xhr.status < 300 || xhr.status == 304) {
                responseObj = JSON.parse(xhr.responseText);
                completionFunction(responseObj);
            } else {
                var errorMessage = xhr.status;
                responseObj = { errorMessages: ["An error of type " + errorMessage + " occurred while attempting to reach the server."] };
                completionFunction(responseObj);
            }
        }
    }
}

感兴趣的行是:

if (xhr.status >= 200 && xhr.status < 300 || xhr.status == 304) {

确定Web Api调用是否成功。如果是，则该函数解析响应并将其输入回调。否则，回调函数将返回一个错误消息。

Ajax函数示例:

var ajax = new Ajax();
var completionFunction = function (data) {
    var returnedData = data;
}
ajax.setGetCompletionFunction(completionFunction);
ajax.getRequest("/api/Home/1");