The correct syntax to call a variable in javascript

Question

I need help.

I have this piece of javascript code:

           // Upload image to sever 
        document.getElementById("upload").addEventListener("click", function(){
            var dataUrl = canvas.toDataURL("image/jpeg", 0.85);
            $("#uploading").show();
            $.ajax({
              type: "POST",
              url: "html5-webcam-save.php",
              data: { 
                 imgBase64: dataUrl,
                 user: "example",
                 userid: " USERNAME "
              }
            }).done(function(msg) {
              console.log("saved");
              $("#uploading").hide();
              $("#uploaded").show();
            });
        });
    }, false);

Within "USERNAME" I need to insert a variable to call the username of the user who is sending the photo.

What is the correct syntax? Thank You

Doesn't make much sense to send a `username` as tje `userid` — putvande, Feb 02 '15 at 13:08
In most cases the server will already know (via whatever authentication system you are using) who the user is, so you shouldn't need to include it in the Ajax request at all. — Quentin, Feb 02 '15 at 13:08
We're all making assumptions here because we don't know where you're getting the username from. Since you're using the "post" method I am assuming that you're submitting a form. If so you can use `userid: $('input[name="userid"]').val();` You're also mixing VanillaJS with jQuery which is not necessary. — Jay Blanchard, Feb 02 '15 at 13:09

score 0 · Answer 1 · edited May 23 '17 at 11:43

If you use Cookie or Session:

There isn't a difference between an AJAX request and a regular page request. It's just another request to the server. When the request is made, the PHP session might still be active and you could reuse the username from there - on server side. Same applies to cookies.

Having that said: most of the time you simply don't need to fetch and insert the username on client-side and pass it to server-side via the ajax request.
If you are not using Cookie or Session:

Then you need a mechanism to (a) insert/pass the username or id into the page and (b) fetch it for the ajax request (this is your question).

There are multiple ways to the transfer data from PHP to JS. One would be to use a hidden input box and insert the username as a value, like explained in the other answer. But you might also insert the username as the value of a JS variable or fill the value into a JSON element. In general, this question has been thoroughly answered before: How to pass variables and data from PHP to JavaScript?

You find good examples on how to get the values from an input box in the following answer: https://stackoverflow.com/a/11563667/1163786 The answer also contains how to fetch the value by using jQuery Selector's, like with ID, Class or Name.

Keep in mind, that you need to secure this, because someone could just insert another id or name into the ajax request on client-side.

score -1 · Answer 2 · edited Feb 02 '15 at 13:42

-1

If you really want to do what your are doing, this might help.

I am assuming you have a separate js file.

Place your USERNAME into a hidden input.

<input type="hidden" id="USERNAME" value="<? echo $USERNAME; ?>">

Then call the value and place that value in your ajax code.

var USERNAME = $('#USERNAME').val();

edited Feb 02 '15 at 13:42

Jens A. Koch

39,862
13
113
141

answered Feb 02 '15 at 13:14

Jason

931
2
12
26

@Jens-AndréKoch Downvotes: "this answer is not useful". Nobody owes more of an explanation than that, stop posting such comments. – user229044 Feb 02 '15 at 14:32

The correct syntax to call a variable in javascript

2 Answers2