refactored localStorage into storage module for frontend

frontend/src/storage.js

@@ -0,0 +1,66 @@
+const { isFile } = require('./utils');
+
+class Storage {
+  constructor(engine) {
+    this.engine = engine 
+  }
+  
+  get totalDownloads() {
+    return Number(this.engine.getItem('totalDownloads'));
+  }
+  set totalDownloads(n) {
+    this.engine.setItem('totalDownloads', n);
+  }
+  get totalUploads() {
+    return Number(this.engine.getItem('totalUploads'));
+  }
+  set totalUploads(n) {
+    this.engine.setItem('totalUploads', n);
+  }
+  get referrer() {
+    return this.engine.getItem('referrer');
+  }
+  set referrer(str) {
+    this.engine.setItem('referrer', str);
+  }
+  
+  get files() {
+    const fs = [];
+    for (let i = 0; i < this.engine.length; i++) {
+      const k = this.engine.key(i);
+      if (isFile(k)) {
+        fs.push(JSON.parse(this.engine.getItem(k))); // parse or whatever else
+      }
+    }
+    return fs;
+  }
+
+  get numFiles() {
+    let length = 0;
+    for (let i = 0; i < this.engine.length; i++) {
+      const k = this.engine.key(i);
+      if (isFile(k)) {
+        length += 1;
+      }
+    }
+    return length;
+  }
+
+  getFileById(id) {
+    return this.engine.getItem(id);
+  }
+  
+  has(property) {
+    return this.engine.hasOwnProperty(property);
+  }
+
+  remove(property) {
+    this.engine.removeItem(property);
+  }
+  
+  addFile(id, file) {
+    this.engine.setItem(id, JSON.stringify(file));
+  }
+}
+
+module.exports = Storage;