Javascript data transformation

Question

Input:

     {
    "8": [{
        "a": true,
        "b": {
            "xyz": 1
        }
    }, {
        "a": false,
        "b": {
            "xyz": 2
        }
    }],
    "13": [{
        "b": {
            "xyz": 4
        }
    }]
 }

Output:

    {
    "8": [{
        "b": {
            "xyz": 2
        }
    }]
 }

How can remove first element of each key and return the few keys of the same object using javascript and lodash library?

Answer 1

You could use reduce the entries returned by Object.entries() like this:

let obj={"8":[{"a":!0,"b":{"xyz":1}},{"a":!1,"b":{"xyz":2}}],"13":[{"b":{"xyz":4}}]}

let output = Object.entries(obj).reduce((acc, [key, value]) => {
  if(value.length > 1)
    acc[key] = value.slice(1)
  
  return acc;
}, {})

console.log(output)

If you want to mutate the original object, loop through the object using for...in and use shift and delete like this:

let obj={"8":[{"a":!0,"b":{"xyz":1}},{"a":!1,"b":{"xyz":2}}],"13":[{"b":{"xyz":4}}]}

for (let key in obj) {
  obj[key].shift()
  if (obj[key].length === 0)
    delete obj[key]
}

console.log(obj)