Ignore falsy header values and improve ajaxHeaders documentation

src/openseadragon.js

@@ -2189,7 +2189,10 @@ function OpenSeadragon( options ){
 
                 if (headers) {
                     Object.keys(headers).forEach(function (headerName) {
-                        request.setRequestHeader(headerName, headers[headerName]);
+                        // Falsy header values will be ignored
+                        if (headers[headerName]) {
+                            request.setRequestHeader(headerName, headers[headerName]);
+                        }
                     });
                 }
 

src/tiledimage.js

@@ -81,7 +81,6 @@
  *      Defaults to the setting in {@link OpenSeadragon.Options}.
  * @param {Object} [options.ajaxHeaders={}]
  *      A set of headers to include when making tile AJAX requests.
- *      Note that these headers will be merged over any headers specified in {@link OpenSeadragon.Options}.
  */
 $.TiledImage = function( options ) {
     var _this = this;

src/tilesource.js

@@ -582,6 +582,9 @@ $.TileSource.prototype = {
      * Responsible for retrieving the headers which will be attached to the image request for the
      * region specified by the given x, y, and level components.
      * This option is only relevant if {@link OpenSeadragon.Options}.loadTilesWithAjax is set to true.
+     * The headers returned here will override headers specified at the Viewer or TiledImage level.
+     * Specifying a falsy value for a header will clear its existing value set at the Viewer or
+     * TiledImage level (if any).
      * @function
      * @param {Number} level
      * @param {Number} x

src/viewer.js

@@ -1239,6 +1239,7 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
      * @param {Object} [options.ajaxHeaders]
      *      A set of headers to include when making tile AJAX requests.
      *      Note that these headers will be merged over any headers specified in {@link OpenSeadragon.Options}.
+     *      Specifying a falsy value for a header will clear its existing value set at the Viewer level (if any).
      * requests.
      * @param {Function} [options.success] A function that gets called when the image is
      * successfully added. It's passed the event object which contains a single property:

test/demo/customheaders.html

@@ -58,14 +58,14 @@
             ajaxHeaders: {
                 // Example of using the viewer-level ajaxHeaders option
                 // for providing an authentication token.
-                'Authentication': 'Bearer MY_AUTH_TOKEN'
+                "Authentication": "Bearer MY_AUTH_TOKEN"
             }
         });
 
         viewer.addTiledImage({
             // The headers specified here will be combined with those in the Viewer object (if any)
             ajaxHeaders: {
-                "X-My-TileSource-Header": "Something"
+                "X-My-TiledImage-Header": "Something"
             },
             tileSource: myCustomTileSource
         });