var A = [ 

     { 

       id: 12345,

       folder: 'folder1',

       name: 'Name1'

     },

     { 

       id: 12346,

       folder: 'folder1',

       name: 'Name2'

     },

     { 

       id: 12347,

       folder: 'folder1',

       name: 'Name3'

     },

     { 

       id: 12348,

       folder: 'folder1',

       name: 'Name4'

     }

    ];

​

var B = [123485, 1234789];

​

function findBy(array, search) {

  var res = [],

      arrayLen  = array.length,

      searchLen = search.length,

      i, j;

  for (i = 0; i < arrayLen; i++) {

    if (~search.indexOf(array[i].id)) {

      res.push(array[i].folder + '/' + array[i].name);  

    }    

  }

  return res;

}

​

​

console.log(findBy(A, B));

​