The attempt to retrieve property descriptors of Node.prototype using Object.getOwnPropertyDescriptors()

Question

The attempt to retrieve property descriptors of Node.prototype using Object.getOwnPropertyDescriptors()

As I keep track of errors on a webpage that utilizes JavaScript, an issue arises when running the following code:

JSON.stringify(
      Object.getOwnPropertyDescriptors(Node.prototype)
    );

An error is thrown stating:

undefined is not a function

I suspect this occurs when the page is loaded via a WebView rather than a standard browser.

To investigate further, I tested the page on both a normal browser and a WebView test app within an Android Emulator - it worked without any problems.

What other steps can I take to troubleshoot this recurring error?

Edit

To gather more information, I added additional logging and inspected the following:

Object.getOwnPropertyDescriptor(Node.prototype, "childNodes");
Object.getOwnPropertyDescriptor(Node.prototype, "parentNode");
Object.getOwnPropertyDescriptor(Node.prototype, "hasChildNodes");

Interestingly, only the hasChildNodes property returns a value.

javascript webview

Answer 1

Answer №1

It seems that in certain browser or webview versions, either the function JSON.stringify or (more likely) Object.getOwnPropertyDescriptors is not supported (the former was introduced in ES5, while the latter came later in ES2017).

What other steps can I take to troubleshoot this issue?

You can add tests and print out the user agent string:

if (!JSON.stringify) {
    /* ...output a message indicating that `JSON.stringify` is not available along with the `navigator.userAgent`...*/
} else if (!Object.getOwnPropertyDescriptors) {
    /* ...output a message indicating that `Object.getOwnPropertyDescriptors` is not available along with the `navigator.userAgent`...*/
} else {
    /* ...output the result of `JSON.stringify(Object.getOwnPropertyDescriptors(Node.prototype))`... */
}

In one of your comments, you inquired:

Is there a way to access the getter function childNodes from the Node.prototype in any browser? In all my testing scenarios (mobile emulators and browsers), it always appears as a direct property of Node.prototype.

If you're encountering undefined when trying to retrieve the descriptor for childNodes using

Object.getOwnPropertyDescriptor(Node.prototype, "childNodes")

in an unconventional implementation, you might need to iterate through the inheritance chain using Object.getPrototypeOf:

function getDescriptor(obj, name) {
    let descr;
    while (obj && !(descr = Object.getOwnPropertyDescriptor(obj, name))) {
        obj = Object.getPrototypeOf(obj);
    }
    return descr;
}

In that case, you would utilize

const childNodesDescriptor = getDescriptor(Node.prototype, "childNodes");

or something similar.

Keep in mind that objects provided by the host like Node.prototype are allowed to deviate from certain rules. It's possible that there are implementations where accessing that getter simply isn't feasible.

Answer 2

It seems that in certain browser or webview versions, either the function JSON.stringify or (more likely) Object.getOwnPropertyDescriptors is not supported (the former was introduced in ES5, while the latter came later in ES2017).

What other steps can I take to troubleshoot this issue?

You can add tests and print out the user agent string:

if (!JSON.stringify) {
    /* ...output a message indicating that `JSON.stringify` is not available along with the `navigator.userAgent`...*/
} else if (!Object.getOwnPropertyDescriptors) {
    /* ...output a message indicating that `Object.getOwnPropertyDescriptors` is not available along with the `navigator.userAgent`...*/
} else {
    /* ...output the result of `JSON.stringify(Object.getOwnPropertyDescriptors(Node.prototype))`... */
}

In one of your comments, you inquired:

Is there a way to access the getter function childNodes from the Node.prototype in any browser? In all my testing scenarios (mobile emulators and browsers), it always appears as a direct property of Node.prototype.

If you're encountering undefined when trying to retrieve the descriptor for childNodes using

Object.getOwnPropertyDescriptor(Node.prototype, "childNodes")

in an unconventional implementation, you might need to iterate through the inheritance chain using Object.getPrototypeOf:

function getDescriptor(obj, name) {
    let descr;
    while (obj && !(descr = Object.getOwnPropertyDescriptor(obj, name))) {
        obj = Object.getPrototypeOf(obj);
    }
    return descr;
}

In that case, you would utilize

const childNodesDescriptor = getDescriptor(Node.prototype, "childNodes");

or something similar.

Keep in mind that objects provided by the host like Node.prototype are allowed to deviate from certain rules. It's possible that there are implementations where accessing that getter simply isn't feasible.

The attempt to retrieve property descriptors of Node.prototype using Object.getOwnPropertyDescriptors()

Answer №1

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