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@ykhrustalev
Forked from picode7/ LocalStorage.ts
Created March 25, 2018 13:48
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LocalStorage TypeScript Module
/**
* Check if localStorage is supported const isSupported: boolean
* Check if localStorage has an Item function hasItem(key: string): boolean
* Get the amount of space left in localStorage function getRemainingSpace(): number
* Get the maximum amount of space in localStorage function getMaximumSpace(): number
* Get the used space in localStorage function getUsedSpace(): number
* Get the used space of an item in localStorage function getItemUsedSpace(): number
* Backup Assosiative Array interface Backup
* Get a Backup of localStorage function getBackup(): Backup
* Apply a Backup to localStorage function applyBackup(backup: Backup, fClear: boolean = true, fOverwriteExisting: boolean = true)
* Dump all information of localStorage in the console function consoleInfo(fShowMaximumSize: boolean = false)
*/
module LocalStorage {
/**
* Flag set true if the Browser supports localStorage, widthout affecting it
*/
export const isSupported: boolean = (() => {
try {
let itemBackup = localStorage.getItem("")
localStorage.removeItem("");
localStorage.setItem("", itemBackup);
if (itemBackup === null) localStorage.removeItem("")
else localStorage.setItem("", itemBackup)
return true;
} catch (e) {
return false;
}
})()
/**
* Check if localStorage has an Item / exists with the give key
* @param key the key of the Item
*/
export function hasItem(key: string): boolean {
return localStorage.getItem(key) !== null
}
/**
* This will return the left space in localStorage without affecting it's content
* Might be slow !!!
*/
export function getRemainingSpace(): number {
let itemBackup = localStorage.getItem("")
let increase = true
let data = "1"
let totalData = ""
let trytotalData = ""
while (true) {
try {
trytotalData = totalData + data
localStorage.setItem("", trytotalData);
totalData = trytotalData;
if (increase) data += data
} catch (e) {
if (data.length < 2) {
break;
}
increase = false
data = data.substr(data.length / 2)
}
}
if (itemBackup === null) localStorage.removeItem("")
else localStorage.setItem("", itemBackup)
return totalData.length
}
/**
* This function returns the maximum size of localStorage without affecting it's content
* Might be slow !!!
*/
export function getMaximumSpace(): number {
let backup = getBackup()
localStorage.clear()
let max = getRemainingSpace()
applyBackup(backup)
return max
}
/**
* This will return the currently used size of localStorage
*/
export function getUsedSpace(): number {
let sum = 0
for (let i = 0; i < localStorage.length; ++i) {
let key = localStorage.key(i)
let value = localStorage.getItem(key)
sum += key.length + value.length
}
return sum
}
/**
* This will return the currently used size of a given Item, returns NaN if key is not found
* @param key
*/
export function getItemUsedSpace(key: string): number {
let value = localStorage.getItem(key)
if (value === null) {
return NaN
} else {
return key.length + value.length
}
}
/**
* Associative-array for localStorage holding key->value
*/
export interface Backup {
[index: string]: string
}
/**
* This will return a localStorage-backup (Associative-Array key->value)
*/
export function getBackup(): Backup {
let backup: Backup = {}
for (let i = 0; i < localStorage.length; ++i) {
let key = localStorage.key(i)
let value = localStorage.getItem(key)
backup[key] = value
}
return backup
}
/**
* This will apply a localStorage-Backup (Associative-Array key->value)
* @param backup associative-array
* @param fClear optional flag to clear all existing storage first. Default: true
* @param fOverwriteExisting optional flag to replace existing keys. Default: true
*/
export function applyBackup(backup: Backup, fClear: boolean = true, fOverwriteExisting: boolean = true) {
if (fClear == true) {
localStorage.clear()
}
for (let key in backup) {
if (fOverwriteExisting === false && backup[key] !== undefined) {
continue
}
let value = backup[key]
localStorage.setItem(key, value)
}
}
/**
* This functions dumps all keys and values of the local Storage to the console,
* as well as the current size and number of items
* @param fShowMaximumSize optional, flag show maximum size of localStorage. Default: false
*/
export function consoleInfo(fShowMaximumSize: boolean = false) {
let amount = 0
let size = 0
for (let i = 0; i < localStorage.length; ++i) {
let key = localStorage.key(i)
let value = localStorage.getItem(key);
console.log(amount, key, value)
size += key.length + value.length
amount++
}
console.log("Total entries:", amount)
console.log("Total size:", size)
if (fShowMaximumSize === true) {
let maxSize = getMaximumSpace()
console.log("Total size:", maxSize)
}
}
}
/*
// Example
console.log("LocalStorage supported:", LocalStorage.isSupported)// true - I hope so anyways 😉
localStorage.setItem("asd", "ASDASD") // sets / overwrites the item "asd"
localStorage.setItem("asd" + Math.random(), "ASDASD") // set another item each time you refresh the page
var backup = LocalStorage.getBackup() // creates a backup, we will need it later!
console.log(JSON.stringify(backup)) // this is how the backup looks like
var usedSpace = LocalStorage.getUsedSpace() // amount of space used right now
console.log("Used Space:", usedSpace)
var maxSpace = LocalStorage.getMaximumSpace() // amount of maximum space aviable
console.log("Maximum Space:", maxSpace)
var remSpace = LocalStorage.getRemainingSpace() // amount of remaining space
console.log("Remaining Space:", remSpace)
console.log("SpaceCheck", maxSpace === usedSpace + remSpace) // true
console.log("hasItem", LocalStorage.hasItem("nothis0ne")) // we don't have this one in our localStorage
localStorage.clear() // oops, we deleted the localStorage!
console.log("has asd",LocalStorage.hasItem("asd")) // item asd is lost 😒
LocalStorage.applyBackup(backup) // but we have a backup, restore it!
LocalStorage.consoleInfo() // show all the info we have, see the backup worked 😊
*/
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