Micro-optimize action binding by preallocating arguments array

[aduth]

It doesn't seem I can easily edit or fork the referenced benchmark, but in the latest Chrome (78), this appears to perform slightly better than the current implementation:

Benchmark details

Setup:

const store7 = createStore();
let viaPreallocated = (function viaPreallocated(store, action) {
    return function() {
        let args = new Array(arguments.length + 1);
        args[0] = store.getState();
        for (let i=0; i<arguments.length; i++) args[i+1] = arguments[i];
        return a7(args);
    };
})(store7, 'viaPreallocated');

Test:

viaPreallocated('a');
viaPreallocated('b');
viaPreallocated(1, 2);
viaPreallocated({});

It's a technique we use in our state library's selector binding.

The size bump is bigger than expected, not significant, but enough to fail tests without adjusting the permitted bundle size.

[aduth]

I managed to reclaim a few bytes in 5f4fbdb by switching to a while loop.

	full/preact.js	dist/unistore.js	preact.js
master	760b	355b	546b
eeec990	777b	373b	546b
5f4fbdb	773b	366b	546b

I tried a few other ideas (unsuccessfully) as well:

• Trying to attain the optimization from length assignment while avoiding explicit assignment of state.

let args = [ state ];
args.length = arguments.length;

This regressed on the benchmarked gains. I assume it's because the benefit comes from the constructor of an array with length.

• Moving ret assignment to the top of the function.

Interestingly, this uses 2 fewer characters before gzip, but ultimately results in a larger gzipped bundle size (diff).

[lkmill]

@aduth hello stranger. i opened a couple of pull requests with rather substantial changes that i personally think greatly improves unistore and was looking for some feedback on. i'm assuming @developit is busy and meanwhile i was hoping to get this feedback from elsewhere. since you have opened a pull request yourself i assume you are familiar with the package and would love to hear what you think about the changes i propose. you can find them at https://github.com/developit/unistore/pull/182 and https://github.com/developit/unistore/pull/183. the second one builds upon the changes from the first.