Split readFile callback into load/error functions.

This improves reject handling.

Author: blueimp

js/load-image-meta.js

@@ -97,16 +97,11 @@
       if (
         !loadImage.readFile(
           loadImage.blobSlice.call(file, 0, maxMetaDataSize),
-          function (e) {
-            if (e.target.error) {
-              // FileReader error
-              return reject(e.target.error)
-            }
+          function (buffer) {
             // Note on endianness:
             // Since the marker and length bytes in JPEG files are always
             // stored in big endian order, we can leave the endian parameter
             // of the DataView methods undefined, defaulting to big endian.
-            var buffer = e.target.result
             var dataView = new DataView(buffer)
             // Check for the JPEG marker (0xffd8):
             if (dataView.getUint16(0) !== 0xffd8) {
@@ -168,6 +163,7 @@
             }
             resolve(data)
           },
+          reject,
           'readAsArrayBuffer'
         )
       ) {

js/load-image.js

@@ -48,6 +48,33 @@
     }
   }
 
+  /**
+   * Loads a given File object via FileReader interface.
+   *
+   * @param {Blob} file Blob object
+   * @param {Function} onload Load event callback
+   * @param {Function} [onerror] Error/Abort event callback
+   * @param {string} [method=readAsDataURL] FileReader method
+   * @returns {FileReader|boolean} Returns FileReader if API exists, else false.
+   */
+  function readFile(file, onload, onerror, method) {
+    if (!$.FileReader) return false
+    var reader = new FileReader()
+    reader.onload = function () {
+      onload.call(reader, this.result)
+    }
+    if (onerror) {
+      reader.onabort = reader.onerror = function () {
+        onerror.call(reader, this.error)
+      }
+    }
+    var readerMethod = reader[method || 'readAsDataURL']
+    if (readerMethod) {
+      readerMethod.call(reader, file)
+      return reader
+    }
+  }
+
   /**
    * Loads an image for a given File object.
    *
@@ -140,14 +167,13 @@
           img.src = url
           return img
         }
-        return loadImage.readFile(file, function (e) {
-          var target = e.target
-          if (target && target.result) {
-            img.src = target.result
-          } else if (reject) {
-            reject(e)
-          }
-        })
+        return readFile(
+          file,
+          function (url) {
+            img.src = url
+          },
+          reject
+        )
       }
     }
     if ($.Promise && typeof callback !== 'function') {
@@ -179,24 +205,8 @@
     callback(img, data)
   }
 
-  // Loads a given File object via FileReader interface,
-  // invokes the callback with the event object (load or error).
-  // The result can be read via event.target.result:
-  loadImage.readFile = function (file, callback, method) {
-    if ($.FileReader) {
-      var fileReader = new FileReader()
-      fileReader.onload = fileReader.onerror = callback
-      // eslint-disable-next-line no-param-reassign
-      method = method || 'readAsDataURL'
-      if (fileReader[method]) {
-        fileReader[method](file)
-        return fileReader
-      }
-    }
-    return false
-  }
-
   loadImage.global = $
+  loadImage.readFile = readFile
   loadImage.createObjectURL = createObjectURL
   loadImage.revokeObjectURL = revokeObjectURL