Accept头在javascript中的应用

我试图在json文件中插入一个Accept头。但我不知道为什么测试不起作用。你能帮助我吗？这是我的密码：

function doJSONRequest(type, url, headers, data, callback){
var r = new XMLHttpRequest();
if(type && url && headers && callback && (arguments.length == 5)){
    r.open(type, url, true);
    if((type != "GET") && (type != "POST") && (type != "PUT") && (type != "DELETE")){
        throw new Error('The value is not recognized')
    } else if((type == "POST") || (type == "PUT") || (type == "GET") || (type == "DELETE")) {
        try {
            if(data === undefined) {
                data = null;
            }
            else if(typeof data === 'object'){
                r.send(JSON.stringify(data));
            } else {
                throw new Error("The data is undefined")
            }
        } catch (e) {
            throw new Error("The data has no JSON format")
        }
    } else if((type == "POST") || (type == "PUT")){

        r.setRequestHeader("Content-type","application/json");
        r.send(JSON.stringify(data));
    }

下面是我使用的测试：

var expectedGETHeader = {
    "Accept": "application/json"
}

doJSONRequest("GET", baseUrl, headers, null, callback1);

setTimeout(function(){
    QUnit.start();
    assert.deepEqual(requests[4].requestHeaders, expectedGETHeader, "should set the \"Accept\": \"application/json\" header for GET requests");
},100);

你能帮我传一下吗？具体错误是：

should set the "Accept": "application/json" header for GET requests
Expected:   
{
    "Accept": "application/json"
}
Result:     
{}
Diff:   
{
     "Accept": "application/json"
} {} 

解决方案 打开代码行后添加代码行

---

r、 setRequestHeader（“接受”、“应用程序/json”）

我没有看到

Accept

标题被设置到任何地方。也许您可以在调用

r.send（JSON.stringify（data））之前就这样做，如下所示：

        if(data === undefined) {
            data = null;
        }
        else if(typeof data === 'object'){
            r.setRequestHeader('Accept', 'application/json'); // <-- this was added
            r.send(JSON.stringify(data));
        } else {
            throw new Error("The data is undefined")
        }

if（数据===未定义）{
数据=空；
}
else if（数据类型==='object'）{
r、 setRequestHeader（'Accept'，'application/json'）//