How to merge multiple array of object by ID in javascript?

Question

I want to merge 4 array of object into one array

For example: 4 arrays like

var arr1 =[
  { memberID : \"81fs\", RatingCW:4.5},
  {          


        

Answer 1

Here's some steps using lodash:

1. Put all objects into an array (_.flatten then _.groupby)
2. Flatten 2d array into 1d array of 'user' obj (_.map then _.merge and apply to pass in array as arg)

var arr1 =[
  { memberID : "81fs", RatingCW:4.5},
  { memberID : "80fs", RatingCW:4},
  { memberID : "82fs", RatingCW:5 },
  { memberID : "83fs", RatingCW:3},
  { memberID : "84fs", RatingCW:4.7}
];
var arr2 =[
  { memberID : "80fs", ratingWW: 4},
  { memberID : "81fs", ratingWW: 4.5},
  { memberID : "83fs", ratingWW: 3},
  { memberID : "82fs", ratingWW: 5},
  { memberID : "84fs", ratingWW: 3.5}
];

var arr3 =  [
  { memberID : "80fs", incoCW:4},
  { memberID : "81fs", incoCW:4.5},
  { memberID : "82fs", incoCW:5},
  { memberID : "83fs", incoCW:3},
  { memberID : "84fs", incoCW:4.5}
  ];
var arr4 =  [
  { memberID : "80fs", incoWW:3},
  { memberID : "81fs", incoWW:2.5 },
  { memberID : "82fs", incoWW:5 },
  { memberID : "83fs", incoWW:3 },
  { memberID : "84fs", incoWW:6.5 }
];

var a  = _.groupBy(_.flatten([arr1,arr2,arr3,arr4]), 'memberID');
var b = _.map(a, function(val){ return _.merge.apply(_,val) });    
console.log(b);