在创建子对象的同时添加键/值对

Question

I am new to working with objects. I want to:

1. Add a key
2. Add a sub-object to that key
3. Push the key/value pair to this sub-object.

For example, the data structure I am looking to achieve would be:

invalidFields = {
    "_0" : {
        "firstName" : "foo",
        "lastName" : "la",
    }
}

The addition of the most nested key/value pair is done by iterating and comparing, so in essence it needs to be added to "_0", not overwriting it.

So far I have:

let invalidFields = {}; // this is initialised outside of the for loop
...
const field = "foo";
const passengerIdentifier = "_" + passengerIndex; // "_0"
const fieldKey = "firstName";
invalidFields[passengerIdentifier] = field;

This adds the key/value pair of "firstName": "foo" but when the loop continues it therefore overwrites it so the data I get is only field applied :

invalidFields = {
    "_0" : "foo",
}

This is obviously not correct as I need the key/value pairs to add to the "_0" sub-object. What am I doing wrong?

Edit: Here is an example of what I have now, but this does not seem to work, the field part isn't added:

const passengerIdentifier = '_'+passengerIndex;
if (!invalidFields[passengerIdentifier]) {
    Object.assign(invalidFields, { [passengerIdentifier] : '' });
    Object.assign(invalidFields[passengerIdentifier], { [fieldKey]: field });
}

Answer 1

To add key/value pair to each sub-object use the following approach:

...
var field = "foo",
    passengerIdentifier = "_" + passengerIndex, // "_0"
    fieldKey = "firstName";

// assuring sub-object with certain `passengerIdentifier`
invalidFields[passengerIdentifier] = invalidFields[passengerIdentifier] || {};
invalidFields[passengerIdentifier][fieldKey] = field;

Answer 2

You could use Object.assign and add the new key/value to the existing object in the loop.

// outside of the loop
invalidFields[passengerIdentifier] = {};

// inside of the loop
Object.assign(invalidFields[passengerIdentifier], { [fieldKey]: field });

Just for completeness, it is possible, to assign a value directly to an object

// inside of the loop
invalidFields[passengerIdentifier][fieldKey] = field;

Answer 3

    let invalidFields = {}; // this is initialised outside of the for loop
    ...
    const field = "foo";
    const passengerIdentifier = "_" + passengerIndex; // "_0"
    const fieldKey = "firstName";

    var subObject = {
         'key1' : value1,
         'key2' : value2,
         // add all keys
     }

    invalidFields[passengerIdentifier] = subObject ;

Answer 4

Does this do what you're trying to achieve?

invalidFields[passengerIdentifier] = { 
  [fieldKey]: field 
}