Remove value from object without mutation

Question

What\'s a good and short way to remove a value from an object at a specific key without mutating the original object?

I\'d like to do something like:

Answer 1

As suggested in the comments above if you want to extend this to remove more than one item from your object I like to use filter. and reduce

eg

    const o = {
      "firstname": "Jane",
      "lastname": "Doe",
      "middlename": "Kate",
      "age": 23,
      "_id": "599ad9f8ebe5183011f70835",
      "index": 0,
      "guid": "1dbb6a4e-f82d-4e32-bb4c-15ed783c70ca",
      "isActive": true,
      "balance": "$1,510.89",
      "picture": "http://placehold.it/32x32",
      "eyeColor": "green",
      "registered": "2014-08-17T09:21:18 -10:00",
      "tags": [
        "consequat",
        "ut",
        "qui",
        "nulla",
        "do",
        "sunt",
        "anim"
      ]
    };

    const removeItems = ['balance', 'picture', 'tags']
    console.log(formatObj(o, removeItems))

    function formatObj(obj, removeItems) {
      return {
        ...Object.keys(obj)
          .filter(item => !isInArray(item, removeItems))
          .reduce((newObj, item) => {
            return {
              ...newObj, [item]: obj[item]
            }
          }, {})
      }
    }

    function isInArray(value, array) {
      return array.indexOf(value) > -1;
    }

Answer 2

For my code I wanted a short version for the return value of map() but the multiline/mutli operations solutions were "ugly". The key feature is the old void(0) which resolve to undefined.

let o2 = {...o, age: 31, lastname: void(0)};

The property stays in the object:

console.log(o2) // {firstname: "Jane", lastname: undefined, age: 31}

but the transmit framework kills it for me (b.c. stringify):

console.log(JSON.stringify(o2)) // {"firstname":"Jane","age":31}