Large memory leaks.

Describe the bug

Hey! Been using anime in A-Frame, an open source WebVR framework. Love it. Though there is a lot of memory leak that can lead to GC pauses.

Taken from a few seconds from the anime homepage, it’s allocated hundreds of kilobytes of memory garbage.

This issue can be alleviated for free with these practices:

• Cache regexes (https://github.com/juliangarnier/anime/blob/master/src/index.js#L69 https://github.com/juliangarnier/anime/blob/master/src/index.js#L358) rather than allocating new one each call
• Use for loops rather than Array.forEach which allocates an entire function (https://github.com/juliangarnier/anime/blob/master/src/index.js#L779)
• Try to avoid array helpers such as Array.map and Array.filter and Array.reduce and Object.keys as these will allocate a new array (https://github.com/juliangarnier/anime/blob/master/src/index.js#L1209 https://github.com/juliangarnier/anime/blob/master/src/index.js#L321).
• Avoid allocating arrays in critical codepaths, reusing a helper / auxiliary array when possible. A single array can be reused by clearing the length array.length = 0; (https://github.com/juliangarnier/anime/blob/master/src/index.js#L959 https://github.com/juliangarnier/anime/blob/master/src/index.js#L308)
• Try to avoid cloning objects (https://github.com/juliangarnier/anime/blob/master/src/index.js#L337)

This is something I could try to help out with.

To Reproduce Steps to reproduce the behavior:

1. Go to anime homepage (or any anime animation).
2. Open devtools memory / performance.
3. Record memory.

Expected behavior Little memory garbage / allocations.

Desktop (please complete the following information):

• OS: macOS
• Browser firefox

[ngokevin]

I believe this issue should be constrained to memory leaks versus unit testing, linting, and Typescript.

[juliangarnier]

Alright, I’m going to focus on this for 3.1. I created a branch called memory plumbing, any help on this is welcome! Thanks !