javascript - How to change a value in nested array - Stack Overflow

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Code:

let fruits = [{
    name: 'apple',
    attributes: [{
        type: 'Granny Smith',
        color: 'green',
        isFavorite: true
      },
      {
        type: 'Ambrosia',
        color: 'red',
        isFavorite: true
      }
    ],
    isFavorite: true
  },
  {
    name: 'Pear',
    attributes: [{
        type: 'Asian',
        color: 'brown',
        isFavorite: true
      },
      {
        type: 'White Pear',
        color: 'white',
        isFavorite: false
      }
    ],
    isFavorite: true
  },
]

const fruitChecked = fruits.map(fruit => {
  return { ...fruit,
    isFavorite: true
  }
})

const fruitAttributesChecked = fruitChecked.map(fruit => {


  (fruit.attributes).map(attr => {
    return { ...attr,
      isFavorite: true
    }

  })
})

console.log(fruits)
console.log(fruitChecked)
console.log(fruitAttributesChecked)

Code:

let fruits = [{
    name: 'apple',
    attributes: [{
        type: 'Granny Smith',
        color: 'green',
        isFavorite: true
      },
      {
        type: 'Ambrosia',
        color: 'red',
        isFavorite: true
      }
    ],
    isFavorite: true
  },
  {
    name: 'Pear',
    attributes: [{
        type: 'Asian',
        color: 'brown',
        isFavorite: true
      },
      {
        type: 'White Pear',
        color: 'white',
        isFavorite: false
      }
    ],
    isFavorite: true
  },
]

const fruitChecked = fruits.map(fruit => {
  return { ...fruit,
    isFavorite: true
  }
})

const fruitAttributesChecked = fruitChecked.map(fruit => {


  (fruit.attributes).map(attr => {
    return { ...attr,
      isFavorite: true
    }

  })
})

console.log(fruits)
console.log(fruitChecked)
console.log(fruitAttributesChecked)

I am trying to change ALL the isFavorite value to true within each object and the isFavorite value within attributes to true.

However I'm getting something similar to this for [undefined,undefined] for fruitAttributesChecked

The oute I desire is below for fruitAttributesChecked

fruitAttributesChecked =
[
   {name: 'apple', 
    attributes: [
          {type: 'Granny Smith', color:'green', isFavorite: true},
          {type: 'Ambrosia', color:'red', isFavorite: true}
    ], 
     isFavorite: true
   },
   {name: 'Pear', 
    attributes: [
          {type: 'Asian', color:'brown', isFavorite: true},
          {type: 'White Pear', color:'white', isFavorite: false}
    ], 
     isFavorite: true
   },
]

What am I missing here?

• javascript
• arrays
• nested
• array.prototype.map

Share Improve this question Follow edited Aug 18, 2021 at 23:02 Barmar 784k5757 gold badges548548 silver badges659659 bronze badges asked Aug 18, 2021 at 22:56 Cartileo Cartileo 311 silver badge44 bronze badges 3

• 2 You're not returning the value of (fruit.attributes).map – Barmar Commented Aug 18, 2021 at 23:03
• Sorry new to this. That makes sense, I have to return ``` (fruit.attributes).map(attr => { return { ...attr, isFavorite: true } ``` – Cartileo Commented Aug 18, 2021 at 23:04
• @Robson thats a typo. the desired should have all true – Cartileo Commented Aug 18, 2021 at 23:05

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 4

You can use a nested map() to return a modified attributes array in the object.

let fruits = [{
    name: 'apple',
    attributes: [{
        type: 'Granny Smith',
        color: 'green',
        isFavorite: true
      },
      {
        type: 'Ambrosia',
        color: 'red',
        isFavorite: true
      }
    ],
    isFavorite: true
  },
  {
    name: 'Pear',
    attributes: [{
        type: 'Asian',
        color: 'brown',
        isFavorite: true
      },
      {
        type: 'White Pear',
        color: 'white',
        isFavorite: false
      }
    ],
    isFavorite: true
  },
]

const fruitChecked = fruits.map(fruit => ({ ...fruit,
  isFavorite: true,
  attributes: fruit.attributes.map(attribute => ({ ...attribute,
    isFavorite: true
  }))
}))

console.log(fruitChecked);

const mappedFruits = fruits.map(fruit => {
    return {
        ...fruit,
        isFavorite: true,
        attributes: attributes.map(attribute => {
            return {
                ...attribute,
                isFavorite: true,
            }
        })
    }
})

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