Huauauaa/cheat-sheet#73 defineProperty

test/prototype.test.js

@@ -0,0 +1,24 @@
+import * as assert from 'assert';
+
+describe('prototype', function () {
+  const foo = { id: 1, name: 'foo' };
+  foo.__proto__.bar = 'bar';
+  it('for in', function () {
+    for (const key in foo) {
+      console.log(key);
+    }
+    assert.strictEqual(foo.bar, 'bar');
+  });
+  it('keys', function () {
+    Object.keys(foo).forEach((key) => console.log(key));
+  });
+
+  it('writable', function () {
+    Object.defineProperty(foo, 'id', { writable: false });
+    // TypeError: Cannot assign to read only property 'id' of object '#<Object>'
+    // foo.id = 2;
+    foo.name = 'foo1';
+    assert.strictEqual(foo.id, 1);
+    assert.strictEqual(foo.name, 'foo1');
+  });
+});