node 遞迴建立檔案

function mkdir(fileString,cb){
		let f_ary = fileString.split('/');
		let index =0;
		function next(){
			if(index==f_ary.length){
				return cb()
			}	
			let path = f_ary.slice(0,index++).join('/');
			fs.accessSync(path,(err)=>{
				if(err){
					fs.mkdir(path,(err,data)=>{
						next();
					})
				}else{
					next();
				}
			})
		}
		next();
}
mkdir('a/b/c',cb)