如何循环访问IndexedDB中的存储键

Question

我正在为IndexedDB使用localForage，我需要遍历存储键，但不是全部。我只需要遍历以名称"field-“开头的键。例如: field-1，field-2，field-3，...

Answer 1

从我发现的情况来看，不可能获得存储中的所有可用密钥。但是，由于您在某个时刻设置了localforage的所有键，也许您可以单独存储这些键。

// storing a new key, could be wrapped inside of a function and included anywhere you update localforage
const newKey = "abc"
const availableKeys = localforage.getItem('keys')
  .then((keys = []) => { // localforage will return undefined if the key does not already exists, this will set it do an empty array by default
    // check here if key is already in keys (using Array.find)
    // push the key that you want to add
    keys.push(newKey)
    // now update the new keys array in localforage
    localforage.setItem('keys', keys)
  })

这样做之后，您就可以使用它来迭代所有可用的键

localforage.getItem('keys')
  .then((keys = []) => {
    keys.forEach(key => {
      // you could not check if the key has you pattern
      if (key.indexOf("field-") > -1) // key has "field-", now do something
    })
  })

由于您不希望遍历所有键，因此可以再次使用filter函数单独存储子集

localforage.getItem('keys')
  .then((keys = []) => {
    // fiter all keys that match your pattern
    const filteredKeys = keys.filter(key => key.indexOf("field-") > -1)
    // store filtered keys in localeforage
    localforage.setItem("filteredKeys", filteredKeys)
  })

Answer 2

localforage.iterate(function(value, key, iterationNumber) {
  if (key.indexOf("field-") > -1) {
    // do something
  }
});