Creating nested arrays of set structure

Question

I have an array of objects with named keys as follows:

Array1 [
  {
    'town1': 'London', // string
    'town2': 'Paris', // string
    'distance': 123456, // number
  },
  {
    'town1': 'Seoul', // string
    'town2': 'Tokio', // string
    'distance': 654321, // number
  },
  {},{},... // Objects with same properties
]

Note that there might be objects without these keys. They should be skipped.
Having all this I want to create a new Array of arrays with 2 objects inside with the following rigid structure:

Array2 [
  [{ name: 'town1', value: 'distance'}, { name: 'town2'}],
  [{ name: 'town1', value: 'distance'}, { name: 'town2'}],
  [{...}, {...}],   // All other objects with existing town1-town2-distance
]

How one could achieve it in the most efficient and fast way?

Answer 1

Ok, I want to have my try as well! Why did nobody think about reduce? It's faster than for-loop! And more elegant. IMO at least.

So I've done few tests, and here are results:

And heres the code:

1) Array.prototype.reduce() with Array.prototype.push()

const array2 = array1.reduce((arr, obj) => {
  if (obj.hasOwnProperty('town1') && obj.hasOwnProperty('town2') && obj.hasOwnProperty('value')) {
    arr.push([ { name: obj.town1, value: obj.distance }, { name: obj.town2 } ])
  }

  return arr
}, [])

2) Array.prototype.reduce() with Array.prototype.concat()

const array2 = array1.reduce((arr, obj) => (
  (obj.hasOwnProperty('town1') && obj.hasOwnProperty('town2') && obj.hasOwnProperty('value'))
    ? Array.prototype.concat(arr, [[ { name: obj.town1, value: obj.distance }, { name: obj.town2 } ]])
    : arr
  ), [])

3) Array.prototype.reduce() with spread operator

array2 = array1.reduce((arr, obj) => (
  (obj.hasOwnProperty('town1') && obj.hasOwnProperty('town2') && obj.hasOwnProperty('value'))
    ?  [...arr, [ { name: obj.town1, value: obj.distance }, { name: obj.town2 } ]]
    : arr
  ), [])

4) And @Emueeus go. For-loop with Array.prototype.push()

for (let i = 0; i<array1.length; i++) {
  if (array1[i].hasOwnProperty('town1') && array1[i].hasOwnProperty('town2') && array1[i].hasOwnProperty('distance')) {
    array2.push([{name:array1[i]['town1'], value: array1[i]['distance']}, { name: array1[i]['town2']}])
  }
}

Here's the test: http://jsfiddle.net/4bca0g2u/