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 [email protected] www.isiahmeadows.com _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
