Question

I would like to create about 10 XML HTTP requests as below. I would like to use the value of i for the first “children” reference, but as i changes before the callback is executed, the value of i mismatches the url taken in “results” tab. How can I generalize this?

var i = 1;
WinJS.xhr({
    url: root.results[i].profile_image_url_https,
    responseType: 'blob'
}).done(function (result) {
    var imgTag = theDiv.children[1].children[0];
    var imageBlob = URL.createObjectURL(result.response, {
        oneTimeOnly: true
    });
    imgTag.src = imageBlob; //tempLocalUrl;
});

i = 2;

WinJS.xhr({
    url: root.results[i].profile_image_url_https,
    responseType: 'blob'
}).done(function (result) {
    var imgTag = theDiv.children[2].children[0];
    var imageBlob = URL.createObjectURL(result.response, {
        oneTimeOnly: true
    });
    imgTag.src = imageBlob; //tempLocalUrl;
});

Answer 1

the typical way is to use an extra function (immediately executed) to capture the current value of your loop variable, e.g.:

var i = 1;

WinJS.xhr({
    url: root.results[i].profile_image_url_https,
    responseType: 'blob'
}).done(function (inner_i) {
  // return the actual callback
  return function (result) {
    // use `inner_i` as needed
    var imgTag = theDiv.children[1].children[0];
    var imageBlob = URL.createObjectURL(result.response, {
      oneTimeOnly: true
    });
    imgTag.src = imageBlob; //tempLocalUrl;
  };
}(i)); // <= pass outer `i`