Spreadsheet implementation on Proxy

Author: tshemsedinov

JavaScript/3-proxy.js

@@ -0,0 +1,70 @@
+'use strict';
+
+const ROWS = 5;
+const columns = ['A', 'B', 'C', 'D', 'E', 'F'];
+const data = {};
+
+const table = new Proxy(data, {
+  get(obj, key) {
+    console.log('get', key);
+    const cell = obj[key];
+    return cell ? cell.value : '';
+  },
+  set(obj, key, value) {
+    console.log('set', key, value);
+    const type = typeof value;
+    if (type === 'function') {
+      const expression = value;
+      value = expression();
+      obj[key] = { value, expression };
+    } else {
+      obj[key] = { value };
+    }
+    return true;
+  }
+});
+
+// Usage
+
+table.A1 = 'city';
+table.B1 = 'population';
+table.C1 = 'area';
+table.D1 = 'density';
+table.E1 = 'country';
+table.F1 = 'relative';
+
+table.A2 = 'Shanghai';
+table.B2 = 24256800;
+table.C2 = 6340;
+table.D2 = 3826;
+table.E2 = 'China';
+
+table.A3 = 'Beijing';
+table.B3 = 21516000;
+table.C3 = 16411;
+table.D3 = 1311;
+table.E3 = 'China';
+
+table.A4 = 'Delhi';
+table.B4 = 16787941;
+table.C4 = 1484;
+table.D4 = 11313;
+table.E4 = 'India';
+
+table.D5 = () => Math.max(table.D2, table.D3, table.D4);
+
+table.F2 = () => Math.round(table.D2 * 100 / table.D5) + '%';
+table.F3 = () => Math.round(table.D3 * 100 / table.D5) + '%';
+table.F4 = () => Math.round(table.D4 * 100 / table.D5) + '%';
+
+const output = [];
+
+for (let i = 2; i <= ROWS; i++) {
+  const row = {};
+  output[i] = row;
+  for (const col of columns) {
+    row[col] = table[col + i];
+  }
+}
+
+console.table(output);