const flatten = require('tree-flatten');
  const tree = {
    name: 'root-1',
    children: [{
      name: 'root-1-1'
    }, {
      name: 'root-1-2',
      children:[{
        name: 'root-1-2-1'
      }]
    }]
  };

  flatten(tree, 'children')
  /* =>
  [
    { name: 'root-1' },
    { name: 'root-1-1' },
    { name: 'root-1-2' },
    { name: 'root-1-2-1' },
  ]
  */