[Olga27]

Я не знаю в чем дело по прежнему, не работает в режиме реального времени, код setInterval я заменила на setTimeout, как советовали выше.

Вот пример:

function init()
{
  
  Index1 = -1;
  bool = true;
  
  var timer = setTimeout(function ajaxQuery(){
    
  
      var ajaxhttp = new XMLHttpRequest();
      var url = "./data.json";
      
      ajaxhttp.open("GET",url,true);
      ajaxhttp.setRequestHeader("content-type","application/json");
      
      
      ajaxhttp.onreadystatechange = function(){
        if(ajaxhttp.readyState == 4 && ajaxhttp.status == 200){
          //console.log(ajaxhttp.responseText);
          jsontent = JSON.parse(ajaxhttp.responseText);
          
          
          
          tree.innerHTML = "";
          const html = recursiveList(jsontent);
          tree.append(html);
          
           output.innerHTML = "<strong>"+bool+"</strong> " + i +" == "+Index1;
           
           posts = jsontent["response"];
           
           if(bool)
           {
              
              switch(Index1) {
                case -1:  // if (x === 'value1')
                  posts[i].status = "current";
                  break;
               default:
                 if(posts.length-1<i)
                 {
                  i = 0;
                 }
                  if(Index1 >= posts[i].photo.length)
                  {
                    posts[i].status = "ok";
                    i++;
                    Index1 = -2; 
                  }
                  else
                  {
                    posts[i].photo[Index1].big.status = "ok";
                  }
                  if(posts[i]==undefined)
                  {
                    bool = false;
                  }
                  break;
                
            
            }
              jsontent["response"] =  posts;
              
              const jsonString = JSON.stringify(jsontent);
              const xhr = new XMLHttpRequest();
              xhr.open("POST",'receive.php');
              xhr.setRequestHeader("Content-Type","application/json");
              xhr.send(jsonString);  
              Index1++;
           }
        }
      }
      
      ajaxhttp.send();
      setTimeout(ajaxQuery,1000);

  },1000);
  
  //setInterval(test,1000);
  
  
  
}

Также php файл я тоже изменила:

<?php
$myFile = "data.json";
$last_modified  = filemtime( $myFile );

$modified_since = ( isset( $_SERVER["HTTP_IF_MODIFIED_SINCE"] ) ? strtotime( $_SERVER["HTTP_IF_MODIFIED_SINCE"] ) : false );
$etagHeader     = ( isset( $_SERVER["HTTP_IF_NONE_MATCH"] ) ? trim( $_SERVER["HTTP_IF_NONE_MATCH"] ) : false );

 


$requestPayload = file_get_contents("php://input");
$object = json_decode($requestPayload,true);




  $etag     = sprintf( '"%s-%s"', $last_modified, md5( $myFile ) );


  header( "Last-Modified: ".gmdate( "D, d M Y H:i:s", $last_modified )." GMT" );

  header( "Etag: ".$etag );


  if ( (int)$modified_since === (int)$last_modified && $etag === $etagHeader ) {
    header( "HTTP/1.1 304 Not Modified" );
    exit;
  }


file_put_contents($myFile,$requestPayload);

?>