perf: replace startsWith with ===

[sun0day]

Description

This pr use str[0] === 'x' instead of str.startsWith('x') for better perf. We can prove that:

• === should be faster according to startsWith source in theory

• perf test data[0] === 'x' wins most of the time

I also test the initial vite dev startup time five times with this repo before and after this PR

test(ms)	1st	2nd	3rd	4th	5th
before pr	2406	2314	2079	1914	1686
after pr	2305	2216	2025	1949	1565

It improves!

Additional context

I guess we can use str[str.length - 1] === 'x' rather than str.endsWith('x') too.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the PR Title Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

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[patak-dev]

Awesome! I didn't expect the perf diff of this change alone to be noticeable 🙌🏼
I think the endsWith is worth doing at least if it is in a hot path.

[sun0day]

Awesome! I didn't expect the perf diff of this change alone to be noticeable 🙌🏼 I think the endsWith is worth doing at least if it is in a hot path.

I will give it a shot.