Proposal: `Object.isEmpty(value)`

Jordan Harband ljharb at
Thu Feb 14 06:54:04 UTC 2019

`Reflect.ownKeys(x || {}).length === 0`?

On Wed, Feb 13, 2019 at 10:31 PM Isiah Meadows <isiahmeadows at>

> This would be roughly equivalent to `Object.keys(value).length === 0`,
> but with a few exceptions:
> 1. If `value` is either `null` or `undefined`, it gracefully falls
> back to `false` instead of throwing an error.
> 2. It takes enumerable symbols into account, like `Object.assign`.
> So more accurately, it returns `false`  if the value is neither `null`
> nor `undefined` and has an own, enumerable property, or `true`
> otherwise.
> It's something I sometimes use when dealing with object-based hash
> maps (like what you get from JSON, input attributes). I typically fall
> back to the (partially incorrect) `for ... in` with a `hasOwnProperty`
> check for string keys, but I'd like to see this as a built-in.
> There's also a performance benefit: engines could short-circuit this
> for almost everything with almost no type checks. It's also an obvious
> candidate to specialize for types.
> - If it's not a reference type (object or function), return `true`.
> - If it's not a proxy object, or a proxy object that doesn't define
> `getPropertyDescriptor` or `ownKeys`, it's often just a memory load,
> even with dictionary objects and arrays.
> - If it's a proxy object with `ownKeys` and/or
> `getOwnPropertyDescriptor`, this is the slow path, but you can still
> short-circuit when `ownKeys` returns an empty array.
> -----
> Isiah Meadows
> contact at
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