LRUCache throws "Invalid array length" as an error if float value is passed to it

[trivikr]

Describe the issue

LRUCache throws "Invalid array length" as an error if float value is passed to it.

Steps to reproduce

Run the following code with mnemonist@0.38.3

const LRUCache = require("mnemonist/lru-cache");
const cache = new LRUCache(1.01);

Observed behavior

The following error is thrown:

  this.K = typeof Keys === 'function' ? new Keys(capacity) : new Array(capacity);
                                                             ^

RangeError: Invalid array length
    at new LRUCache (/Users/trivikr/workspace/lru-cache/node_modules/mnemonist/lru-cache.js:47:62)
    at Object.<anonymous> (/Users/trivikr/workspace/lru-cache/index.js:3:15)
    at Module._compile (internal/modules/cjs/loader.js:1068:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1097:10)
    at Module.load (internal/modules/cjs/loader.js:933:32)
    at Function.Module._load (internal/modules/cjs/loader.js:774:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
    at internal/main/run_main_module.js:17:47

Expected behavior

A custom error can be thrown on this line instead after adding a check for integer:

mnemonist/lru-cache.js

Lines 40 to 41 in 825538a

	if (typeof this.capacity !== 'number' || this.capacity <= 0)
	throw new Error('mnemonist/lru-cache: capacity should be positive number.');

[trivikr]

Example fix without changing the prior error:

  if (typeof this.capacity !== 'number' || this.capacity <= 0)
    if (!isFinite(this.capacity) || Math.floor(this.capacity) !== this.capacity)
      throw new Error('mnemonist/lru-cache: capacity should be a finite positive integer.');
    throw new Error('mnemonist/lru-cache: capacity should be positive number.');

[Yomguithereal]

Hello @trivikr. Looks good to me. Do you want to open a PR with this change?

[trivikr]

Do you want to open a PR with this change?

PR posted at #166