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Nested Destructuring in JavaScript or Node.js

JavaScript introduced the destructuring assignment back in 2015. The destructuring assignment is a way to unpack properties of an object or items from arrays into variables using a syntax that looks like objects or arrays.

This tutorial shows you how to use nested destructuring in JavaScript.

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Using Nested Destructuring in JavaScript

The concept of destructuring assignments applies recursively in JavaScript. You can destructure properties from an object or array from the root level and also from nested levels.

Here’s an example using nested destructuring to retrieve properties from an exemplary user object:

const user = {  
  nested: { 
    a: 'foo',
    b: [
      'first item',
      'second item',
      'third item',
    ]
  }
}

const {  
  nested: {
    a,
    b: [first, , third]
  }
} = user

console.log({ a, first, third })  
// {
//   a: 'foo',
//   first: 'first item',
//   third: 'third item'
// }

Destructuring nested properties follows the way of assigning key-value-pairs in an object. The difference is that you’re using this way on the left side of the equal sign:

const { nested: { something } } = sourceObject

Please notice in the example that you can also destructure nested arrays and skip values. The example retrieves the first and third item from the b array.

That’s it!

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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