perf: preinitialize typeCheck RegExp

[SebastianSpeitel]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe: Performance improvement

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

After looking at the performance of one of my apps, I noticed, the function, that took the most time summed up was getType() , defined in [1] taking 200ms. I noticed the regular expression getting created for each call and measured again including the proposed improvement, which took the time down to 150ms. To make sure I changed it back to confirm and it again timed at 200ms.

[1]

vue/src/core/util/props.js

Lines 182 to 185 in b07087d

	function getType (fn) {
	const match = fn && fn.toString().match(/^\s*function (\w+)/)
	return match ? match[1] : ''
	}

[SebastianSpeitel]

Maybe further improvements could be made by removing the regular expression completely and using standard string manipulation methods.

[SebastianSpeitel]

Is there anything else, that needs to be done before merging? @posva

[posva]

@SebastianSpeitel You don't need to do anything else, thank you :)

[SebastianSpeitel]

I made this PR 2 months ago. Is there a reasons for this taking so long?

[lefreet]

@SebastianSpeitel cached it may be better ?

  const getType = cached(function getType (fn) {
    var match = fn && fn.toString().match(/^\s*function (\w+)/);
    return match ? match[1] : ''
  })

[SebastianSpeitel]

@SebastianSpeitel cached it may be better ?

  const getType = cached(function getType (fn) {
    var match = fn && fn.toString().match(/^\s*function (\w+)/);
    return match ? match[1] : ''
  })

Both could be optimal.
Compile the regex only once and compute the type of each object only once.

[lefreet]

but the fn.toString is a expense also, for every function @SebastianSpeitel sorry my later comment

[tophf]

Why not just type.name instead of the entire getType?