Langdon wrote:
Something that simply wraps this all-to-common code:
var key;
for (key in obj) {
if (obj.hasOwnProperty(key) === true) {
...
}
}
Imo the problem is not that there is no wrapper method for this pattern,
but that this code is all too common. It should rarely be needed, and is
mostly wrong anyway.
The cases to consider are
* You use `obj` as a dictionary. If you want to safeguard against
inherited properties, you use `obj = Object.create(null)`. Those objects
don't even have a `.hasOwnProperty` method.
And with ES6, a `Map` is a better solution anyway.
* You are enumerating array keys. To safeguard against inherited
properties from `Array.prototype`, you should not use `hasOwnProperty`
but rather use the proper loop type that iterates indices instead.
* You are processing JSON. `JSON.parse`'d objects inherit only from
`Object.prototype` which does not have enumerable properties anyway.
* You are processing (JSON/dictionary) objects and fear that someone
added enumerable properties to `Object.prototype`. Well, that's their
fault, not your loop's one. If the environment is broken, your code is
as well; there's nothing you can - and need - to do against.
* You are processing arbitrary objects with unknown prototype chains. To
skip inherited properties in a `for in` loop, the only safe approach is
to use `if (Object.prototype.hasOwnProperty.call(obj, key))` or avoid
the drama altogether via `Object.keys`/`Object.getOwnProperty…`.
The last case is the only one where you'd really need `hasOwnProperty`.
The proliferation of `if (obj.hasOwnProperty(key))` needs to be stopped,
it's cargo cult programming at best.
Regards,
Bergi
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