flattening using concatAll method

var movieLists = [{
      name: "New Releases",
      videos: [{
        "id": 70111470,
        "title": "Die Hard",
        "rating": 4.0
      }, {
        "id": 654356453,
        "title": "Bad Boys",
        "rating": 5.0
      }]
    }, {
      name: "Dramas",
      videos: [{
        "id": 65432445,
        "title": "The Chamber",
        "rating": 4.0
      }, {
        "id": 675465,
        "title": "Fracture",
        "rating": 5.0
      }]
    }]

var flattenArr = []

Array.prototype.concatAll = function(){
  var output = []
  
  this.forEach(function(item) {
    if (Array.isArray(item)) 
      item.forEach((result) => output.push(result))
    else 
      output.push(item)
  })
  
  return output
}

flattenArr = movieLists.map(item => {
  return item.videos.map(video => {
    return video.id
    // console.log(video.id)
  })
}).concatAll()

console.log(flattenArr)