Answers for "merge array of objects with same key python"

how to merge 2 object array by the same key with lodash

Lodash
var a = [
  { userId:"p1", item:1},
  { userId:"p2", item:2},
  { userId:"p3", item:4}
];

var b = [
  { userId:"p1", profile:1},
  { userId:"p2", profile:2},
  { userId:"p4", profile:4}
];
var merged = _.merge(_.keyBy(a, 'userId'), _.keyBy(b, 'userId'));
var values = _.values(merged);
console.log(values);
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merge 2 dictionaries with same keys javascript

const target = { a: [1], b: [2] };
const source = { a: [2], c: [5] };

const returnedTarget = Object.assign(target, source);

for(var date in source)
target[date] = [...target[date] || [],...source[date]]

console.log(target);