hasOwnProperty does not work for MessageEvent object
hasOwnProperty does not work for MessageEvent object
I don't understand why hasOwnProperty does not work for some special JavaScript Objects like MessageEvent (I don't know if there are others, If you know please let me know).
hasOwnProperty
MessageEvent
const message = new MessageEvent('worker', data: 'hello' );
message.hasOwnProperty('data'); // false
console.log(message.data); // 'hello'
'data' in message // true
How can I be sure data is inside message? If I use in is tricky because data can exists in the inherited objects and in returns true for that case as well.
data
message
in
in
true
I really want to know if data exists as a property there... because you can do data: undefined so your check will fail... even if data is there defined as undefined.
– V. Sambor
Aug 31 at 10:12
A
MessageEvent object always has a data property. If you don't specify it explicitly, it defaults to null. So what's the point of checking for it?– Barmar
Aug 31 at 10:17
MessageEvent
data
null
the point is that I have created a function which checks if a nested property exists in an object. And when I want to check message.data.a.b my function fails because data is not recognized... github.com/vsambor/get-value-safely/blob/master/index.js
– V. Sambor
Aug 31 at 10:20
It's not an ordinary object property, it's implemented using a getter method in the prototype.
– Barmar
Aug 31 at 10:23
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how about, (typeof message.data != 'undefined') ?
– Comirdc
Aug 31 at 10:11