feat(js-checkpoint):add test for freeze exercise

js/tests/freeze_test.js

@@ -0,0 +1,34 @@
+export const tests = []
+const t = (f) => tests.push(f)
+const isConst = (name) => {
+  try {
+    eval(`${name} = 'm'`)
+    return false
+  } catch (err) {
+    return true
+  }
+}
+
+// arr
+t(() => Array.isArray(arr)) // arr is declared and is an array
+t(({ eq }) => eq(arr[0], 4)) // arr first element is 4
+t(({ eq }) => eq(arr[1], '2')) // arr second element is "2"
+t(({ eq }) => eq(arr.length, 2)) // arr length is 2
+
+// obj
+// obj is declared and of type object
+t(() => obj.constructor === Object)
+// obj is constant and can not be re-assigned
+t(({ fail }) => obj && fail(() => (obj = 10)))
+// obj.str is of type string
+t(() => typeof obj.str === 'string')
+// obj.num is of type number
+t(() => typeof obj.num === 'number')
+// obj.bool is of type boolean
+t(() => typeof obj.bool === 'boolean')
+// obj.undef is of type undefined
+t(() => 'undef' in obj && typeof obj.undef === 'undefined')
+
+// check if all variable are const
+t(() => ['arr', 'obj']
+  .every(isConst))