load("test-common.js"); try { assert(Object.isExtensible() === false); assert(Object.isExtensible(undefined) === false); assert(Object.isExtensible(null) === false); assert(Object.isExtensible(true) === false); assert(Object.isExtensible(6) === false); assert(Object.isExtensible("test") === false); let s = Symbol(); assert(Object.isExtensible(s) === false); let o = { foo: "foo" }; assert(Object.isExtensible(o) === true); Object.preventExtensions(o); assert(Object.isExtensible(o) === false); console.log("PASS"); } catch (e) { console.log("FAIL: " + e); }