How to verify if object has specific property without the operator "in"?

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Some browsers do not support inputMode, like Safari. So to then mitigate the situation, I would have another behavior if the inputMode existed or not.

Searching I found the operator in:

if ("inputMode" in document.querySelector("input")) {
  console.log("Existe inputMode no <input>")
}
<input>

It works. The problem is, since I’m using another language, I have no way to call the operator in (well I would have, but it would be a significantly bigger job just for that).

Is there any function that does the same as the in?

How can I have the same behavior as in without using this specific operator? Using any function (other than eval, obviously).

javascript objects property

  • I just don’t quite understand why you can’t use the in. Could you explain it a little better? I was curious.

  • 2

    I’m using Golang, and compiling for Webassembly. Then the querySelector becomes: js.Global().Get("document").Call("querySelector", "input"). I only have access to .Call, .Invoke and .InstanceOf (...), but you don’t have any .In. So I don’t assume there’s no way to use the in. The functions I have access to are those. The "most difficult method" would be to create a Callimport to call my JS function inside the Golang, something like that from here. I withheld that information because it would make everything more confusing.

1 answer

3


You can use the function Reflect.has, which has the same operation as the operator in, only in a qualified function format in the overall object Reflect.

So:

if (Reflect.has(document.querySelector("input"), "inputMode")) {
  console.log(1);
}

It is worth remembering that the operator in (and therefore Reflect.has) are different from Object.prototype.hasOwnProperty. Learn more in this other answer.

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