improve performance of asNumber

[Uzlopak]

before:

{"n1":1,"n2":null}
number x 43,047,096 ops/sec ±1.45% (183 runs sampled)

after:

node bench
{"n1":1,"n2":null}
number x 1,253,340,543 ops/sec ±0.11% (195 runs sampled)

This is my benchmark:

'use strict'

const Benchmark = require('benchmark')
Benchmark.options.minSamples = 100

const suite = Benchmark.Suite()

const FJS = require('.')
const stringify = FJS({
  type: 'object',
  properties: {
    n1: { type: 'number' },
    n2: { type: 'number' },
  }
})

// const stringify = require('./serialize')

const input = {
  n1: 1,
  n2: Infinity
}
console.log(stringify(input))

suite
  .add('number', () => {
    stringify(input)
  })
  .on('cycle', (event) => {
    console.log(String(event.target))
  })
  .on('complete', () => {})
  .run()

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

lgtm