如何将json_encode数据传递到.js文件？

Question

jquery_auto.js文件

function autocomplete(inp, arr) {
  var currentFocus;
  inp.addEventListener("input", function(e) {
      var a, b, i, val = this.value;
      closeAllLists();
      if (!val) { return false;}
      currentFocus = -1;
      a = document.createElement("DIV");
      a.setAttribute("id", this.id + "autocomplete-list");
      a.setAttribute("class", "autocomplete-items");
      this.parentNode.appendChild(a)
      /*for each item in the array...*/
      for (i = 0; i < arr.length; i++) {
        if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) {
          b = document.createElement("DIV");
          /*make the matching letters bold:*/
          b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>";
          b.innerHTML += arr[i].substr(val.length);
          b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>";
          b.addEventListener("click", function(e) {
              inp.value = this.getElementsByTagName("input")[0].value;
              closeAllLists();
          });
          a.appendChild(b);
        }
      }
  });
  inp.addEventListener("keydown", function(e) {
      var x = document.getElementById(this.id + "autocomplete-list");
      if (x) x = x.getElementsByTagName("div");
      if (e.keyCode == 40) {
        currentFocus++;
        addActive(x);
      } else if (e.keyCode == 38) {
        currentFocus--;
        addActive(x);
      } else if (e.keyCode == 13) {
        e.preventDefault();
        if (currentFocus > -1) {
          if (x) x[currentFocus].click();
        }
      }
  });
  function addActive(x) {
    if (!x) return false;
    removeActive(x);
    if (currentFocus >= x.length) currentFocus = 0;
    if (currentFocus < 0) currentFocus = (x.length - 1);
    x[currentFocus].classList.add("autocomplete-active");
  }
  function removeActive(x) {
    for (var i = 0; i < x.length; i++) {
      x[i].classList.remove("autocomplete-active");
    }
  }
  function closeAllLists(elmnt) {
    var x = document.getElementsByClassName("autocomplete-items");
    for (var i = 0; i < x.length; i++) {
      if (elmnt != x[i] && elmnt != inp) {
        x[i].parentNode.removeChild(x[i]);
      }
    }
  }
  document.addEventListener("click", function (e) {
      closeAllLists(e.target);
  });
}
var countries = "<?php echo ?>";

autocomplete.php文件

<?php
    session_start();
    error_reporting(0);
    include("config.php");
    $sql = mysqli_query($con,"select * from city order by cname");
    while($row = mysqli_fetch_array($sql))
    {
        $data[] = $row['cname'];
    }
    echo json_encode($data);
?>

index.php

<script src="inc/jquery_auto.js"></script>
<script>
    autocomplete(document.getElementById("search"), countries);
</script>
<form autocomplete="off" action="/action_page.php">
    <input type="text" name="search" id="search" placeholder="Search">
</form>

在此代码中，我创建了自动完成文件。如果我仅使用var countries = ["America","Australia","India","UK"]，它就可以正常工作，并在“自动完成”框中显示所有数据。但是，当我创建一个单独的文件autocomplete.php并希望将此文件数据显示到我的jquery_auto.js文件中时，它将不起作用。那么，如何解决这个问题呢？请帮助我。

谢谢