Add getByPlaceholder in the browser module

[ankur22]

What?

This adds a convenience method on page to be able to select on elements with the placeholder attribute.

Why?

This is part of the story of adding getBy*, which makes working with selectors a little easier. We used to have to work with the page.locator API providing either a CSS selector or a XPath selector if we wanted to get the element by the placeholder attribute on an element:

<input placeholder="Enter your name">

const l = page.locator('input[placeholder="Enter your name"]'); // CSS
const l = page.locator('//input[@placeholder="Enter your name"]'); // XPath

Now we can use:

const l = page.getByPlaceholder('Enter your name');

Working with getBy* in general is an industry standard in the frontend testing world.

Checklist

• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have added tests for my changes.
• I have run linter and tests locally (make check) and all pass.

Checklist: Documentation (only for k6 maintainers and if relevant)

Please do not merge this PR until the following items are filled out.

• I have added the correct milestone and labels to the PR.
• I have updated the release notes: link
• I have updated or added an issue to the k6-documentation: grafana/k6-docs#NUMBER if applicable
• I have updated or added an issue to the TypeScript definitions: grafana/k6-DefinitelyTyped#NUMBER if applicable

Related PR(s)/Issue(s)

#4790, #4248

[codebien]

LGTM

[codebien]

What is the expectation on this? If this used with high frequency, I expect we can use a strings builder with a bigger capacity and avoiding re-allocating the string in the case the execution joins the isQuoted branch.

If we need to apply it, then it would require a quick benchmark of buildAttribtuteSelector func.

[ankur22]

I'll work with strings builder, but not in this PR. I've added it as an action item in a catch all issue that I'll work on once all the getBy* PRs are merged in.

The base branch was changed.