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JS Property Descriptors - Interactive Lab | IconVault

Toggle writable, enumerable and configurable on live properties, run real assign and delete attempts, and explore freeze and seal gotchas.

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JS Property Descriptors

Writable, enumerable, configurable plus freeze and seal gotchas

5 of 5 free uses left

Define a property

Live object

id: 1

{ writable: false, enumerable: true, configurable: false }

secret: "shh"

{ writable: true, enumerable: false, configurable: true }

Experiment log

Try assign / Try delete on a property, or run the inspector…

const obj = {};
Object.defineProperty(obj, "id", {
  value: 1,
  writable: false,
  enumerable: true,
  configurable: false,
});
Object.defineProperty(obj, "secret", {
  value: "shh",
  writable: true,
  enumerable: false,
  configurable: true,
});

Object.getOwnPropertyDescriptor(obj, "id");
// {"value":1,"writable":false,"enumerable":true,"configurable":false}

Freeze / seal gotchas, executed live

Frozen array push throws

const arr = Object.freeze([1, 2, 3]);
arr.push(4); // TypeError in strict mode

Freeze is shallow

const obj = Object.freeze({ nested: { a: 1 } });
obj.nested.a = 99; // works! freeze is shallow

Seal allows writes, blocks add/delete

const obj = Object.seal({ a: 1 });
obj.a = 2;      // ok
obj.b = 3;      // TypeError in strict mode
delete obj.a;   // TypeError in strict mode

Non-configurable cannot be redefined

const obj = {};
Object.defineProperty(obj, "id", { value: 1, configurable: false });
Object.defineProperty(obj, "id", { writable: true }); // TypeError

5 of 5 free inspections left. Runs fully in your browser.

About this tool

IconVault's JS Property Descriptors lab makes the hidden flags behind every JavaScript property visible and touchable. Define properties with writable, enumerable and configurable toggles, then run real assignment and delete attempts to see what silently fails in sloppy mode and what throws a TypeError in strict mode. The live object shows Object.keys, JSON.stringify and spread behavior updating as you flip flags. It is free and runs fully in your browser, and your whole session exports as copyable code.

A second section executes the classic freeze and seal gotchas live: pushing to a frozen array, mutating through a shallow freeze, sealing while still allowing writes, and the TypeError from redefining a non-configurable property. These are the exact behaviors that surprise developers in interviews and production bugs, demonstrated with running code instead of documentation quotes.

Frequently asked questions

Popular searches

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