What is the correct way to fix error with Unexpected token F in JSON?

Question

JSON

There is such a piece of code, from the content filter:

var back_url = window.location.pathname;
var back_title = document.title;
var back_speedbar = document.getElementById("dle-speedbar");
$(function(){
  $('body').on('click', '[data-fieldsearch=submit]', function() {
    var $filter_field = $(this).closest('form').serialize();
    window.history.replaceState(null, null, "/");
    ShowLoading("Ищем... ищем... ищем...");
    $.post(dle_root + "engine/ajax/field_search.php", { form_field : $filter_field }, function(data){
      if(data)
      {
        window.history.replaceState(null, null, "/");
        var content = jQuery.parseJSON( data );
        $("#dle-content1").remove();
        $("#dle-content").css("display", "none");
        $("#dle-content").before("<div id=\"dle-content1\">" + content.content + "</div>");
        window.history.replaceState(null, null, content.url);
      }
    });
    HideLoading("");
    return false;
  });
  $('body').on('click', '.field_search_nav > a', function() {
    var $filter_field = $( this ).attr("href");
    window.history.replaceState(null, null, "/");
    ShowLoading("Ищем... ищем... ищем...");
    $.post(dle_root + "engine/ajax/field_search.php", { form_field : $filter_field, filter_nav : 1 }, function(data){
      if(data)
      {
        window.history.replaceState(null, null, "/");
        var content = jQuery.parseJSON( data );
        document.title = content.meta_title;
        $("#dle-speedbar").html(content.speedbar);
        $("#dle-content1").remove();
        $("#dle-content").css("display", "none");
        $("#dle-content").before("<div id=\"dle-content1\">" + content.content + "</div>");
        window.history.replaceState(null, null, content.url);
      }
    });
    HideLoading("");
    return false;
  });
  $( "[data-filtertriger=fieldseacrh]" ).change(function() {
    var $filter_field = $( this ).serialize();
    window.history.replaceState(null, null, "/");
    ShowLoading("Ищем... ищем... ищем...");
    $.post(dle_root + "engine/ajax/field_search.php", { form_field : $filter_field }, function(data){
      if(data)
      {
        window.history.replaceState(null, null, "/");
        var content = jQuery.parseJSON( data );
        $("#dle-content1").remove();
        $("#dle-content").css("display", "none");
        $("#dle-content").before("<div id=\"dle-content1\">" + content.content + "</div>");
        window.history.replaceState(null, null, content.url);
      }
    });
    HideLoading("");
  });
  
  $('body').on('click', '[data-fieldsearch="reset"]', function() {
    window.history.replaceState(null, null, back_url);
    ShowLoading("Секунду...");
    document.title = back_title;
    $("#dle-speedbar").html(back_speedbar);
    $('[data-filtertriger=fieldseacrh] input[type="text"]').each(function(i){
      if($(this).attr('name') != undefined)
      {
        if($(this).attr('name').indexOf('r-') + 1)
        {
          var slider = $(this).data("ionRangeSlider");
          slider.update({
            from: slider.options.min,
            to: slider.options.max
          });
        }
        else
        {
          $(this).val('');
        }
      }
    });
    $('[data-filtertriger=fieldseacrh] select').each(function(i){
      $(this).children('option').each(function(n){
        $(this).attr('selected', false);
      });
    });

    $('[data-filtertriger=fieldseacrh] input[type="radio"], [data-filtertriger=fieldseacrh] input[type="checkbox"]').each(function(i){
      $(this).attr('checked', false);
    });
    $("#dle-content1").remove();
    $("#dle-content").css("display", "block");
    HideLoading("");
    return false;
  });
});

He swears at with such an error:


what to do?

Answer 1

dle_root + "engine/ajax/field_search.php"Instead of JSON, the server at the address returns some text starting with the letter "F".
Open the developer tools (F12), the Network tab (Network) and see what exactly.