Javascript 定期发出 HTTP 请求不起作用

Question

我有一个页面来显示聊天消息。我需要每 30 秒刷新一次聊天正文才能加载新消息。我已将间隔设置为 30 秒，该函数正在运行，但它没有发出 HTTP 请求。这是我的代码

function loadmessages(){

   var ids = document.getElementById("pid").value;
   var request = new XMLHttpRequest();
  request.open("get", '/refresh_message/'+ ids );
  request.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
  request.setRequestHeader("X-CSRF-TOKEN", document.querySelector('meta[name="csrf-token"]').content);
  request.onload = function(){
  if(this.status == 200){
    var resp = JSON.parse(this.responseText);
    console.log(resp.message);

    }
    else{
        console.log(this.status);
    }

request.send(null); 
}


}

loadmessages(); 
setInterval(function(){
    loadmessages() 
}, 30000);

Answer 1

一致的缩进很重要。您将 request.send(null); 放入 request.onload 函数中，所以当然它永远不会首先被发送。尝试将其放在外面:

function loadmessages() {
  var ids = document.getElementById("pid").value;
  var request = new XMLHttpRequest();
  request.open("get", '/refresh_message/' + ids);
  request.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
  request.setRequestHeader("X-CSRF-TOKEN", document.querySelector('meta[name="csrf-token"]').content);
  request.onload = function() {
    if (this.status == 200) {
      var resp = JSON.parse(this.responseText);
      console.log(resp.message);
    } else {
      console.log(this.status);
    }
  }
  request.send(null);
}