gistfile1.js

var _ = require('lodash');
var test_data = [
  { id: 'a', order_by: 1 },
  { id: 'b', order_by: 2 },
  { id: 'c', order_by: 3 },
  { id: 'd', order_by: 4 },
  { id: 'e', order_by: 5 },
  { id: 'f', order_by: 6 },
  { id: 'g', order_by: 7 },
  { id: 'h', order_by: 8 },
  { id: 'i', order_by: 9 }
];

/**
 * reorders an array of objects
 *
 * @param: move {Object} - e.g. {id: 1, order_by: 4} to move 1 to place 4
 * @param: data {Array} - array of objects to reorder
 * @param: key {String} - key to order objects by
 */
function shift_order(move, data, key) {
  if (move[key] > data.length || move[key] < 1)
    return;

  // Move requested element
  data.splice(move[key] - 1, 0, data.splice(_.findIndex(data, {id: move.id}), 1)[0]);
  // Normalize order properties
  data = data.map(function (elem, idx) {
      elem[key] = idx + 1;
  });
}

/**
 * prints array of objects
 */
function print_data(data) {
  for (var index = 0; index < data.length; index++)
    console.log(data[index]);
}

console.log('pre-shift');
print_data(test_data);

shift_order({ id: 'a', order_by: 4 }, test_data, 'order_by');

console.log('post-shift 1');
print_data(test_data);

shift_order({ id: 'f', order_by: 2 }, test_data, 'order_by');

console.log('post-shift 2');
print_data(test_data);