Changing the values inside an object within an array

Question

I am trying extract an array that is inside an object in an array and I want to edit the value of the objects within that extracted array. It seems like this should be simple but I cant figure out why my forEach isnt updating the objects. From what I understand forEach mutates the original array so why isnt this working?

My expected result would be:


      [
          {
            "label": "400 mg",
            "value": "400 mg",
          },
          {
             "label": "600 mg",
             "value": "600 mg",
          },
          {
             "label": "800 mg",
             "value": "800 mg",
          }
      ]

const array1 = [
        {
            "Name": "IBU (oral - tablet)",
            "Strength": [
                {
                    "Strength": "400 mg",
                    "NDC": "55111068201"
                },
                {
                    "Strength": "600 mg",
                    "NDC": "55111068301"
                },
                {
                    "Strength": "800 mg",
                    "NDC": "55111068401"
                }
            ]
        },          
    ];

let newA = array1.map((item) => item.Strength).flatMap((item) => item)

newA.forEach((str) => ({label: str.Strength ,value: str.Strength}))


console.log(newA)

The forEach method executes a provided function once for each array element without having any return. In your forEach you create a new object which does not get used nor returned. newA.forEach((item) => {item.label = item.Strength}) would change the initial object. — Lain
– Lain, Commented Sep 15, 2022 at 14:23
You should not try to use .forEach method on arrays, you are looking for developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… - with this you can achieve your desired result. — Nicolae Maties
– Nicolae Maties, Commented Sep 15, 2022 at 14:23
@NicolaeMaties I see what you mean I was trying not to use .map method over an over. I could just map over the newArr again but I was thinking there might be a better way that doesnt involve creating a new copy of the array. — CourtneyJ
– CourtneyJ, Commented Sep 15, 2022 at 14:32

Nicolae Maties · Accepted Answer · 2022-09-15 14:44:54Z

1

I assume that you are looking for this, using .map not .forEach.

const result = [
        {
            "Name": "IBU (oral - tablet)",
            "Strength": [
                {
                    "Strength": "400 mg",
                    "NDC": "55111068201"
                },
                {
                    "Strength": "600 mg",
                    "NDC": "55111068301"
                },
                {
                    "Strength": "800 mg",
                    "NDC": "55111068401"
                }
            ]
        }    
][0].Strength.map(el => ({ label: el.Strength, value: el.Strength }));

console.log(result);

answered Sep 15, 2022 at 14:44

Nicolae Maties

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Comments

isiPouchi · Accepted Answer · 2022-09-15 14:34:31Z

0

const array1 = [
        {
            "Name": "IBU (oral - tablet)",
            "Strength": [
                {
                    "Strength": "400 mg",
                    "NDC": "55111068201"
                },
                {
                    "Strength": "600 mg",
                    "NDC": "55111068301"
                },
                {
                    "Strength": "800 mg",
                    "NDC": "55111068401"
                }
            ]
        },          
    ];

let newA = array1.map((item) => item.Strength).flatMap((item) => item)

newA.map((str) => {
  str.label= str.Strength ;
  str.value = str.Strength;
  delete str.Strength;
  delete str.NDC
})
console.log(newA)

edited Sep 15, 2022 at 14:34

answered Sep 15, 2022 at 14:28

isiPouchi

111 silver badge3 bronze badges

1 Comment

CourtneyJ Over a year ago

This returns the same value as my attempt. I see what youre trying to do. I think you forgot to assign the second map a var name.

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