[improvement] Uploader: optimize code

packages/uploader/utils.js

@@ -0,0 +1,27 @@
+export function toArray(item) {
+  if (Array.isArray(item)) {
+    return item;
+  }
+
+  return [item];
+}
+
+export function readFile(file, resultType) {
+  return new Promise(resolve => {
+    const reader = new FileReader();
+
+    reader.onload = event => {
+      resolve(event.target.result);
+    };
+
+    if (resultType === 'dataUrl') {
+      reader.readAsDataURL(file);
+    } else if (resultType === 'text') {
+      reader.readAsText(file);
+    }
+  });
+}
+
+export function isOversize(files, maxSize) {
+  return toArray(files).some(file => file.size > maxSize);
+}