The result returned by Array.isArray is false

Question

The result returned by Array.isArray is false

As someone diving into the world of javascript and currently unpacking destructuring, I stumbled upon a puzzling snippet that sparked a question in my mind. After some editing, my code was identified as an array by the console, which left me scratching my head.

1: Why is this not recognized as an array?

const heroes = [{
  lol: ['l', 'Iron Man']
}]

const [lol, dc] = heroes;
console.log(Array.isArray(lol));

2: On the contrary, why is this one flagged as an array?

const heroes = {
  lol: ['l', 'Iron Man']
}

const {lol, dc} = heroes;
console.log(Array.isArray(lol));

javascript arrays json object destructuring

Answer 1

Answer №1

Within the initial code snippet, heroes represents an array where the first element is an object with property lol containing ['l', 'Iron Man'].

{
 lol:['l', 'Iron Man' ]
}

Using destructuring assignment, lol is assigned to this element while dc remains as undefined due to the absence of a second element in the array. As the provided object is not an array, Array.isArray(lol) returns false.

const heroes = [{
 lol:['l', 'Iron Man' ]
}]

const [element1, element2 ] = heroes;
console.log(element1);

In another scenario, heroes portrays an object. Through the destructuring assignment, lol inherits the value from the lol property within the object (['l', 'Iron Man']). Meanwhile, dc is set based on the dc property, which doesn't exist and consequently defaults to undefined. Since lol is associated with an array, Array.isArray(lol) now evaluates to true.

To capture the array from the initial snippet within lol, additional nesting is required.

const heroes = [{
 lol:['l', 'Iron Man' ]
}]

const [{lol, dc}] = heroes;
console.log(Array.isArray(lol));

Answer 2

Within the initial code snippet, heroes represents an array where the first element is an object with property lol containing ['l', 'Iron Man'].

{
 lol:['l', 'Iron Man' ]
}

Using destructuring assignment, lol is assigned to this element while dc remains as undefined due to the absence of a second element in the array. As the provided object is not an array, Array.isArray(lol) returns false.

const heroes = [{
 lol:['l', 'Iron Man' ]
}]

const [element1, element2 ] = heroes;
console.log(element1);

In another scenario, heroes portrays an object. Through the destructuring assignment, lol inherits the value from the lol property within the object (['l', 'Iron Man']). Meanwhile, dc is set based on the dc property, which doesn't exist and consequently defaults to undefined. Since lol is associated with an array, Array.isArray(lol) now evaluates to true.

To capture the array from the initial snippet within lol, additional nesting is required.

const heroes = [{
 lol:['l', 'Iron Man' ]
}]

const [{lol, dc}] = heroes;
console.log(Array.isArray(lol));

Answer 3

Answer №2

When extracting data from the 'heroes' variable, there are two different ways to do it. One involves using const [lol, dc] to assign an object with a key 'lol' and value ['l', 'Iron Man'], while the other uses const {lol, dc} to assign an array ['l', 'Iron Man'].

Answer 4

When extracting data from the 'heroes' variable, there are two different ways to do it. One involves using const [lol, dc] to assign an object with a key 'lol' and value ['l', 'Iron Man'], while the other uses const {lol, dc} to assign an array ['l', 'Iron Man'].

Answer 5

Answer №3

When attempting to destructure in the first example, make sure to use [] for arrays and {} for objects.

In this scenario, start by destructuring the array with [] before moving on to destructure the object within {}.

const heroes = [{
  lol:['l', 'Iron Man' ]
 }]
 
 const [{lol, dr}] = heroes;
 console.log(lol)
 console.log(Array.isArray(lol));

Answer 6

When attempting to destructure in the first example, make sure to use [] for arrays and {} for objects.

In this scenario, start by destructuring the array with [] before moving on to destructure the object within {}.

const heroes = [{
  lol:['l', 'Iron Man' ]
 }]
 
 const [{lol, dr}] = heroes;
 console.log(lol)
 console.log(Array.isArray(lol));

The result returned by Array.isArray is false

Answer №1

Answer №2

Answer №3

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