davedx/delete vs null

## delete vs null
let cache1 = {}, cache2 = {}

const blob = () => {
  var d = []
  for (var i=0; i<10; i++) {
    d[i] = Math.random()
  }
  return d
}

let its = 100000
console.log('iterations: '+its)

for (var i=0; i<its; i++) {
  const idx = `key_${i}`
  cache1[idx] = blob()
  cache2[idx] = blob()
}

// now let's time deletions
let t1 = Date.now()
for (var i=0; i<its; i++) {
  delete cache1[`key_${i}`]
}
console.log(`delete time: ${Date.now()-t1} = ${(Date.now()-t1)/its} ms/op`)

let t2 = Date.now()
for (var i=0; i<its; i++) {
  cache2[`key_${i}`] = null
}
console.log(`null time: ${Date.now()-t2} = ${(Date.now()-t2)/its} ms/op`)