为什么我不能在Rails中使用Ajax？

Question

I started learning Rails 3 months ago.And now I'm trying to add Ajax in my Rails app.

So it have some problems.

In my Index.html.erb file:

<script>
    function loadDoc() {
      var xhttp = new XMLHttpRequest();
      xhttp.onreadystatechange = function() {
        if (xhttp.readyState == 4 && xhttp.status == 200) {
          document.getElementById("demo").innerHTML = xhttp.responseText;
        }
      };
      xhttp.open("GET","demo.txt", true);
      xhttp.send();
    }
</script>

<button type="button" onclick="loadDoc()">click</button>

<p id="demo"></p>

And I created a file that demo.txt.I try to show content in demo.txt when I click the button.But it shows nothing.

So have any tut for me.

Thanks !

Answer 1

The second parameter of the xhttp.open(...) call should be a URL, not simple a file name. If you are running the Rails application with "rails s" then your url might look something like "http://localhost:3000/demo.txt" if the file demo.txt is in your public folder. Without a URL in that second parameter, I suspect that the request is never finding your rails application.

You might also want to dig into jquery (since you tagged it) to understand how to use that library to issue the request. The interface is much simpler than the low-level js.