.waitForFunction() should return a value

It seems that as for now, .waitForFunction() just checks for the truthiness of the returned value in the frame context, which is then discarded. It is impossible to implement any functionality that waits for the function’s Promise actually returning a value and using that value in the Node context.

One possible scenario would be using .waitForFunction to wait for a specific <option> tag with a specific label and returning instead its value.

I could simulate it with .evaluate() but I would lose the polling/timeout configuration options.

Version: 1.0.0-rc Platform: Linux NodeJS:: v9.x

[marco-pragliola]

@yujiosaka Actually, .waitForXPath was the thing I was missing at the beginning. Then, trying some hacks and workarounds, I came up with this question. But yes, it could solve some scenarios.

It is very common to do tests or scraping based on the presence of some inner HTML and not a tag, class or id by itself.

[marco-pragliola]

@yujiosaka but your label attribute makes no sense, it should be value, with label I am referring to the innerHTML of the option. Which is impossible to check via selectors.

Practical example: a page is loaded with a select tag. The dropdown is filled via AJAX with some option tags like:

<option value="45">Foo</option>
<option value="66">Bar</option>

I have to intercept the option whose innerHTML is Foo and retrieve its value (45). I’d expect to do something like:

const retrievedValue = await page.waitForFunction((arg1, arg2, ...) => {
     // fancy stuff here
     return value;
}, options, arg1, arg2, ...);

This would be super because I can pass arguments and specify polling type and timeout. But I have to do some serious hacks to retrieve that value.

This is only a particular case, anyway.