jQuery Ajax call in loop losing local variable reference

I am making several jQuery ajax calls within a loop. Each time one of the ajax calls return I need to reference a value corresponding to the original ajax call. My current code doesn't work properly, in that the value of the lskey variable has been altered by further loop iterati开发者_JAVA技巧ons.

Here is the code:

for (var i = 0, len = localStorage.length; i < len; i++) {
        var lskey = localStorage.key(i);
        if (lskey.substr(0, 4) === 'form') {
            var postdata = localStorage.getItem(lskey); // Get the form data
            $.ajax({
                type: "POST",
                async: "false",
                url: "/Profile/PostForm",
                data: postdata,
                success: function (data) {
                    $('#rollinginfo').append('<br>' + data + ',key=' + lskey);
                    localStorage.removeItem(lskey); // Remove the relevant localStorage entry
                }
            , error: function (data) { $('#rollinginfo').append('<br />ERR:' + data); }
            });


        }
    } 

The problem is that lskey is being altered each time the loop executes, and therefore the success callback does not have a reference to the value of lskey that existed at the time of the call.

How do I reference the correct value of lskey for each success callback?

---

for (var i = 0, len = localStorage.length; i < len; i++) {
    var lskey = localStorage.key(i);
    if (lskey.substr(0, 4) === 'form') {
        var postdata = localStorage.getItem(lskey); // Get the form data
        $.ajax({
            type: "POST",
            async: "false",
            url: "/Profile/PostForm",
            data: postdata,
            local_lskey: lskey
            success: function (data) {
                $('#rollinginfo').append('<br>' + data + ',key=' + lskey);
                localStorage.removeItem(this.local_lskey); // Remove the relevant localStorage entry
            }
        , error: function (data) { $('#rollinginfo').append('<br />ERR:' + data); }
        });
    }
}

This should work.

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In the end I added the key info to the server posting, and then returned it from the server in JSON format so the success function could then simply refer to the key contained in the server response.

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Have you considered chaining the AJAX calls? Basically you can make one AJAX call, process the result, modify lskey, etc. Then when you are ready, increment i and issue the second AJAX call. Loop this way instead of using the for loop...

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You could put your ajax call into its own function and pass the lskey and postData values in. That way localStorage.removeItem(lskey) will refer to the lskey variable in the context of the function rather than the context of the loop.

Example

Declare the function -

function postForm(postdata, lskey) {
  $.ajax({
    type: "POST",
    async: "false",
    url: "/Profile/PostForm",
    data: postdata,
    success: function(data) {
      $('#rollinginfo').append('<br>' + data + ',key=' + lskey);
      localStorage.removeItem(lskey); // Remove the relevant localStorage entry
    },
    error: function(data) {
      $('#rollinginfo').append('<br />ERR:' + data);
    }
  });
}

Then you can call your function from your loop -

for (var i = 0, len = localStorage.length; i < len; i++) {
  var lskey = localStorage.key(i);
  if (lskey.substr(0, 4) === 'form') {
    var postdata = localStorage.getItem(lskey); // Get the form data
    postForm(postdata, lskey);
  }
}

You could also declare the function just before the loop (assigning it to a variable) and then call it within the loop.

var postForm = function(postdata, lskey) {
  $.ajax({
    type: "POST",
    async: "false",
    url: "/Profile/PostForm",
    data: postdata,
    success: function(data) {
      $('#rollinginfo').append('<br>' + data + ',key=' + lskey);
      localStorage.removeItem(lskey); // Remove the relevant localStorage entry
    },
    error: function(data) {
      $('#rollinginfo').append('<br />ERR:' + data);
    }
  });
}
for (var i = 0, len = localStorage.length; i < len; i++) {
  var lskey = localStorage.key(i);
  if (lskey.substr(0, 4) === 'form') {
    var postdata = localStorage.getItem(lskey); // Get the form data
    postForm(postdata, lskey);
  }
}