Performance enhancements

[maxwellgerber]

A few minor performance enhancements

• Don't look in the cacheStore on every function call, keep in local variable
• Don't recreate setData function on every function call
• Set a default key for when args is empty instead of calling JSON.stringify
• Calculate some parameters for maxAge logic ahead of time

Results:
8.3x speedup for empty arguments
1.86x speedup for single arguments
1.1x speedup for complex arguments

Benchmark Code:

const mp = require('./perf');
const m = require('./index');

const argSets = [
  [],
  [0],
  ['foo', 'bar', 'baz'],
  [{foo: true}, {bar: false}]
];

const scenarios = [
  {
    mem: mp,
    name: 'Perf    ',
  },
  {
    mem: m,
    name: 'Original'
  }
];

const N = 1e8;

for (let args of argSets) {
  for (let {mem, name} of scenarios) {
    let i = 0;
    const f = () => i++;
    const memoized = mem(f);
    const title = `${name} - with args: ${JSON.stringify(args)}`;

    console.time(title);
    for (let i = 0; i < N; i++) {
      memoized.call(memoized, ...args)
    }
    console.timeEnd(title);
  }
}

Results:

Perf     - with args: []: 3929.611ms
Original - with args: []: 32624.623ms
Perf     - with args: [0]: 5355.543ms
Original - with args: [0]: 9960.462ms
Perf     - with args: ["foo","bar","baz"]: 44711.881ms
Original - with args: ["foo","bar","baz"]: 49462.724ms
Perf     - with args: [{"foo":true},{"bar":false}]: 66376.395ms
Original - with args: [{"foo":true},{"bar":false}]: 75006.349ms

[sindresorhus]

Very nice! Thanks for doing this :)