Is there a direct way to deeply nest in a JavaScript object? [duplicate]

Question

In other words: can JavaScript automatically create object parents?

In an example where "testObject" is already created...

let testObject = {}

...this throws an error...

testObject.parent.child.grandchild = { foo: 'ya' };

This works but is a lot of code...

  testObject.parent = {};
  testObject.parent.child = {};
  testObject.parent.child.grandchild = { foo: 'ya' };

Things get more complicated if the middle generation might have data, so checks are needed...

  if (!testObject.parent) {
    testObject.parent = {};
  }
  if (!testObject.parent.child) {
    testObject.parent.child = {};
  }
  testObject.parent.child.grandchild = { foo: 'ya' };

What I'm looking for is a direct way to create middle generations in an object if they're not already created. Is this possible with less coding than these examples? (Sorry in advance if this is a duplicate question!)

you call them generations but those are actually properties of objects.. and if you try access to properties of a an undefined value the error thrown is Uncaught TypeError: Cannot read properties of undefined. The point being that if you use a property name not defined in an object, its value will be undefined indeed and you cannot have success when you attempt to access its own properties further. You may be interested to Optional chaining (?.) — Diego D
– Diego D, Commented Feb 8, 2024 at 22:29

Alexander Nenashev · Accepted Answer · 2024-02-08 22:27:11Z

3

??= operator:

const testObject = {};

((testObject.parent ??= {}).child ??= {}).grandchild = {foo: 'ya'};

console.log(testObject);

answered Feb 8, 2024 at 22:27

Alexander Nenashev

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2 Comments

PatrickReagan Over a year ago

Thank you Alexander, that's an elegant solution!

PatrickReagan Over a year ago

For future readers: Alexander's suggestion to use the ??= (nullish coalescing assignment) operator seems to be working well for me. Further reference can be found here... developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

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