let str = '0123456789'
let temp = ''
// 先做一個 10KB 的字符串
while (str.length !== 10240) {
  str = str + '0123456789'
}
// 先清空
localStorage.clear()
const computedTotal = () => {
  return new Promise((resolve) => {
    // 不斷往 LocalStorage 中累積存儲 10KB
    const timer = setInterval(() => {
      try {
        localStorage.setItem('temp', temp)
      } catch {
        // 報錯說明超出最大存儲
        resolve(temp.length / 1024 - 10)
        clearInterval(timer)
        // 統(tǒng)計完記得清空
        localStorage.clear()
      }
      temp += str
    }, 0)
  })
}
(async () => {
  const total = await computedTotal()
  console.log(`最大容量${total}KB`)
})()

最后得出的最大存儲量為5120KB ≈ 5M

已使用容量

計算已使用容量，我們只需要遍歷localStorage身上的存儲屬性，并計算每一個的length，累加起來就是已使用的容量了~~~

const computedUse = () => {
  let cache = 0
  for(let key in localStorage) {
    if (localStorage.hasOwnProperty(key)) {
      cache += localStorage.getItem(key).length
    }
  }
  return (cache / 1024).toFixed(2)
}
(async () => {
  const total = await computedTotal()
  let o = '0123456789'
  for(let i = 0 ; i < 1000; i++) {
    o += '0123456789'
  }
  localStorage.setItem('o', o)
  const useCache = computedUse()
  console.log(`已用${useCache}KB`)
})()

可以查看已用容量

剩余可用容量

我們已經計算出總容量和已使用容量，那么剩余可用容量 = 總容量 - 已使用容量

const computedsurplus = (total, use) => {
  return total - use
}
(async () => {
  const total = await computedTotal()
  let o = '0123456789'
  for(let i = 0 ; i < 1000; i++) {
    o += '0123456789'
  }
  localStorage.setItem('o', o)
  const useCache = computedUse()
  console.log(`剩余可用容量${computedsurplus(total, useCache)}KB`)
})()

可以得出剩余可用容量