index.js
function getMap(id){
            var route = getRoute(id);
            var cache = jsonCache[route];
            if(!cache){
                var filePath = path.join(root, route, 'map.json');
                try{
                    cache = jsonCache[route] = JSON.parse(fs.readFileSync(filePath));
                }catch(e){
                    throw e;
                }
            }
            return cache;
        }
function getMap(id){
            var route = getRoute(id);
            var cache = jsonCache[route];
            if(!cache){
                var filePath = path.join(root, route, 'map.json');
                try{
                    cache = jsonCache[route] = JSON.parse(fs.readFileSync(filePath));
                }catch(e){
                    throw e;
                }
            }
            return cache;
        }
获取id所在json文件的json数据(如果在缓存中找不到对应数据,则读取文件)