simple-lru.js
function (key) {
      var entry = this._byKey.get(key);
      if (entry) {
        this._touch(entry);
        return entry.val;
      }
    }
function (key) {
      var entry = this._byKey.get(key);
      if (entry) {
        this._touch(entry);
        return entry.val;
      }
    }
function ( key ) { var entry = this . _byKey . get ( key ) ; if ( entry ) { this . _touch ( entry ) ; return entry . val ; } }
get cache by key

@param {String}
@return {any} cache if it exists
get cache by key