H 5のlocalStorageローカルキャッシュオブジェクトをカプセル化し、キャッシュ有効期間、キャッシュ本数制限を実現

/*
 *    indexKey    
 *    cacheSize     
 */
  var localCache = new LRUCache(indexKey, cacheSize);

//    ：https://cdn.bootcss.com/crypto-js/3.1.9/crypto-js.js
var CryptoJS = require( 'crypto' );
/**
 * **********************************************************************
 *   ：        LRU  
 *     ：
 *    indexKey    
 *    cacheSize     
 * 
 *   var localCache = new LRUCache(indexKey, cacheSize);
 *     ：
 *     ：localCache.put(key, value, expires);
 *     ： localCache.get(key);
 *     ：localCache.clear();
 *     ：localCache.remove(key);
 *         ：localCache.removeLast();
 * **********************************************************************
 */
/**
 *     
 * @param indexKey    
 * @param cacheSize    
 * @constructor
 */
function LRUCache ( indexKey, cacheSize ) {
  //         
  var expiresTime      = 60 * 24 * 365;
  var currentSize      = 0; //     
  var cacheSize        = cacheSize ; //    
  var keyArray         = [];//    
  var localStorage     = window.localStorage || {
      getItem:function() {
        return null;
      },
      setItem:function() {
      }
    }; //     localStorage      
  indexKey             = sha1( indexKey );
  /**
   *   localStorage    ,           
   */
  keyArray = JSON.parse( getLocalStorage( indexKey ) ) || [];
  currentSize = keyArray.length;
  for ( var i = 0; i < keyArray.length; i++ ) {
    var time    = +keyArray[ i ].time;
    var nowTime = +new Date();
    if ( nowTime > time ) {
      removeLocalStorage( keyArray[ i ].key );
      keyArray.splice( i, 1 );
    }
    saveKeyIndexLocalStorage();
  }
  /**
   * hash  ->sha1  
   * @param str
   */
  function sha1 ( str ) {
    return CryptoJS.SHA1( str ).toString();
  }

  /**
   *        （       ，       ）
   * @author @DYL
   * @DATE 2017-11-21
   */
  function getByteLen ( val ) {
    var len = 0;
    for ( var i = 0; i < val.length; i++ ) {
      var a = val.charAt( i );
      if ( a.match( /[^\x00-\xff]/ig ) != null ) {
        len += 2;
      }
      else {
        len += 1;
      }
    }
    return len;
  }

  function saveKeyIndexLocalStorage ( obj ) {
    if ( obj ) {
      keyArray.unshift( obj );
    }
    localStorage.setItem( indexKey, JSON.stringify( keyArray ) );
  }

  /**
   *       localStorage 
   * @expire      
   * @param obj Object  
   */
  function saveLocalStorage ( key, value ) {
    localStorage.setItem( key, value );
  }

  function removeLocalStorage ( key ) {
    removeLastLocalStorage( key )
  }

  function removeLastLocalStorage ( key ) {
    currentSize--;
    localStorage.removeItem( key );
  }

  function getLocalStorage ( key ) {
    return localStorage.getItem( key );
  }

  /**
   *     
   * @param key
   * @param value
   */
  function put ( key, value, expires ) {
    //               
    var item = get( key );
    value = JSON.stringify( value ); //        JSON
    key   = sha1( key );
    if ( item ) {
      moveToHead( key );
    } else {
      //            .
      if ( currentSize >= cacheSize ) {
        removeLast();
      } else {
        currentSize++;
        expires = expires || expiresTime;
        expires = +new Date() + expires * 60 * 1000; //       
        saveKeyIndexLocalStorage( { key:key, time:expires, size:getByteLen( value ) } );
      }
    }
    saveLocalStorage( key, value );
  }

  /**
   *        
   * @param key
   * @return
   */
  function get ( key ) {
    key = sha1( key );
    moveToHead( key );
    return JSON.parse( getLocalStorage( key ) );
  }

  /**
   *      
   * @param key
   * @return
   */
  function remove ( key ) {
    key = sha1( key );
    for ( var i = 0, len = keyArray.length; i < len; i++ ) {
      if ( key == keyArray[ i ].key ) {
        currentSize--;
        keyArray.splice( i, 1 );
        removeLocalStorage( key );
        saveKeyIndexLocalStorage();
        break;
      }
    }
  }

  /**
   *     cachaName    
   */
  function clear () {
    keyArray    = [];
    currentSize = 0;
    localStorage.clear();
  }

  /**
   *         
   *                
   */
  function removeLast () {
    var key = keyArray.pop();
    removeLastLocalStorage( key );
  }

  /**
   *       ，             
   * @param node
   */
  function moveToHead ( key ) {
    var item = {};
    for ( var i = 0; i < keyArray.length; i++ ) {
      item = keyArray[ i ];
      if ( key == item.key && i != 0 ) {
        //         ，         ，          
        item = keyArray.splice( i, 1 )[ 0 ];
        saveKeyIndexLocalStorage( item );
        break;
      }
    }
  }

  this.get        = get;
  this.put        = put;
  this.remove     = remove;
  this.clear      = clear;
  this.removeLast = removeLast;
  this.moveToHead = moveToHead;
}
window.LRUCache = LRUCache;