计算 LocalStorage 总容量

let str = '0123456789'
let temp = ''
// 先做一个 10KB 的字符串
while (str.length !== 10240) {
  str = str + '0123456789'
}

// 先清空
localStorage.clear()

const computedTotal = () => {
  return new Promise((resolve) => {
    // 不断往 LocalStorage 中累积存储 10KB
    const timer = setInterval(() => {
      try {
        localStorage.setItem('temp', temp)
      } catch {
        // 报错说明超出最大存储
        resolve(temp.length / 1024 - 10)
        clearInterval(timer)
        // 统计完记得清空
        localStorage.clear()
      }
      temp += str
    }, 0)
  })
}

(async () => {
  const total = await computedTotal()
  console.log(`最大容量${total}KB`)
})()