fs创建目录

let fs = require('fs');
function mkdir(paths, callback) {
 paths = paths.split('/');
 let index = 1;
 function next() {
   if (index === paths.length + 1) return callback();
   let dirPath = paths.slice(0, index++).join('/');
   fs.access(dirPath, err => {
     if (err) {
       fs.mkdir(dirPath, next);
     }else{
       next();
     }
   })
 }
 next();
}
mkdir('a/b/c/d',()=>{})