File System 定额（配额查询）

/** * 参考的API: * http://w3c.github.io/quota-api/ *  *///文件系统请求标识 window.requestFileSystem = window.requestFileSystem || window.webkitRequestFileSystem//根据URL取得文件的读取权限 window.resolveLocalFileSystemURL = window.resolveLocalFileSystemURL || window.webkitResolveLocalFileSystemURL//临时储存和永久存储navigator.temporaryStorage = navigator.temporaryStorage || navigator.webkitTemporaryStorage;navigator.persistentStorage = navigator.persistentStorage || navigator.webkitPersistentStorage;//常量const _TEMPORARY = 'temporary', _PERSISTENT = 'persistent'/** * 转为promise，主要是把 a.b(param1,param2,successCallback,errorCall) 转为promise * @param {*期待的是函数} obj  * @param {*上下文} ctx  * @param {*参数} args  */function toPromise(obj, ctx, ...args) {    if (!obj) return obj    //如果已经是Promise对象    if ('function' == typeof obj.then) return obj    //若obj是函数直接转换    if ('function' == typeof obj) return _toPromise(obj)    return obj;    //函数转成 promise    function _toPromise(fn) {        return new Promise(function (resolve, reject) {            fn.call(ctx, ...args, (...ags) => {                //多个参数返回数组，单个直接返回对象                resolve(ags && ags.length > 1 ? ags : ags[0])            }, (err) => {                reject(err)            })        })    }}/** * 查询和申请定额 * 测试脚本： * 使用情况： FileStorageQuota.instance.queryInfo().then(data=>console.log(data)) * 申请空间： FileStorageQuota.instance.requestPersistentQuota().then(data=>console.log(data)) */class FileStorageQuota {    constructor() {        let supportedTypes = [_TEMPORARY, _PERSISTENT];        this.storageQuota = navigator.storageQuota || {            storages: { [_TEMPORARY]: navigator.webkitTemporaryStorage, [_PERSISTENT]: navigator.webkitPersistentStorage },            queryInfo: function (type) {                return toPromise(this.storages[type].queryUsageAndQuota, this.storages[type]).then(arr => {                    return { usage: arr[0], quota: arr[1] }                })            },            requestPersistentQuota: function (requestQuota) {                return toPromise(this.storages[_PERSISTENT].requestQuota, this.storages[_PERSISTENT], requestQuota * 1024 * 1024).then(quota => {                    return { quota }                })            },            supportedTypes        }        this.supportedTypes = supportedTypes        this._instance = null //实例    }    /**     * 获得实例     */    static get instance() {        return !!this._instance ? this._instance : this._instance = new FileStorageQuota()    }    /**     * 已经分配的额度和适用查询     * @param {*类型  window.TEMPORAR(0) |window.PERSISTENT(1) }  type     */    queryInfo(type = window.TEMPORARY) {        return new Promise((resolve, reject) => {            this.storageQuota.queryInfo(this.supportedTypes[type])                .then(storageInfo => resolve({ quota: this.tansferBytes(storageInfo.quota), usage: this.tansferBytes(storageInfo.usage) }))                .catch(this.errorHandler(reject))        })    }    /**     * 请求配额，只有PERSISTENT才需要用户允许，     * 返回值是你请求的和已经分配的大值     * @param {* window.TEMPORAR(0) |window.PERSISTENT(1)} type     * @param {* 请求的配额大小} requestQuota       */    async requestPersistentQuota(requestQuota = 5) {        let { quota: quotaM, usage } = await this.queryInfo(window.PERSISTENT)        if (requestQuota > quotaM) {            return new Promise((resolve, reject) =>                this.storageQuota.requestPersistentQuota(requestQuota * 1024 * 1024)                    .then(storageInfo => {                        return resolve({ quota: this.tansferBytes(storageInfo.quota), usage: this.tansferBytes(storageInfo.usage || usage) })                    })                    .catch(this.errorHandler(reject)))        }        return { quota: Math.max(requestQuota, quotaM), usage }    }    /**     * 把bytes换算成KB,M,G等     * @param {* bytes的长度}  bytesLength     * @param {* 转为目标的单位} target     */    tansferBytes(bytesLength, target = 'M') {        let m = {            'Byte': 0,            'KB': 1,            'M': 2,            'G': 3        }        return bytesLength / Math.pow(1024, m[target] || 0)    }    /**     * Promise里面的错误处理     * @param {*}  reject     */    errorHandler(reject) {        return (error) => {            reject(error)        }    }}

FileStorageQuota.instance.requestPersistentQuota().then(data=>console.log(data))Object {quota: 10240, usage: 0}