How to add aditional object property in array of objects?

Question

I'm trying to dynamically add additional property in the existing object. This is what I have:

let items = [
   {name: 'Carlsberg', category: 'Beer', price: '4.99'},
   {name: 'Smirnoff', category: 'Vodka', price: '28.99'},
   {name: 'Miller Lite', category: 'Beer', price: '7.99'}
]

These are the object properties which I wish to add:

categories:{
     beerCounter:2,
     vodkaCounter:1,
}

And what I want is to dynamically add additional properties of an object to look like this:

items = [
       {name: 'Carlsberg', category: 'Beer', price: '4.99', counter: categories.beerCounter},
       {name: 'Smirnoff', category: 'Vodka', price: '28.99', counter: categories.vodkaCounter},
       {name: 'Miller Lite', category: 'Beer', price: '7.99', counter: categories.beerCounter}
    ]

@ChrisLi I think he wants to mutate in place not create a new array — Jaromanda X
– Jaromanda X, Commented Aug 9, 2022 at 14:26
Try this single line answer : items.forEach(obj => obj.counter = categories[${obj.category.toLowerCase()}Counter]) — Rohìt Jíndal
– Rohìt Jíndal, Commented Aug 9, 2022 at 14:35

isaactfa · Accepted Answer · 2022-08-09 14:29:02Z

1

Using Array.forEach:

let items = [
   {name: 'Carlsberg', category: 'Beer', price: '4.99'},
   {name: 'Smirnoff', category: 'Vodka', price: '28.99'},
   {name: 'Miller Lite', category: 'Beer', price: '7.99'}
];

const categories = {
     beerCounter: 2,
     vodkaCounter: 1,
};

items.forEach(item => {
  item.counter = item.category === 'Beer' ? categories.beerCounter : categories.vodkaCounter;
})

console.table(items);

answered Aug 9, 2022 at 14:29

isaactfa

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1 Comment

Jan Tuđan Over a year ago

Just wanted this, thank you!

Nick · Accepted Answer · 2022-08-09 14:29:10Z

1

You could just iterate your array using forEach, setting the counter property using the lower-cased category value for each item:

let items = [{
    name: 'Carlsberg', category: 'Beer', price: '4.99'
  },
  {
    name: 'Smirnoff', category: 'Vodka', price: '28.99'
  },
  {
    name: 'Miller Lite', category: 'Beer', price: '7.99'
  }
]

let categories = {
  beerCounter: 2,
  vodkaCounter: 1,
}

items.forEach(i => i.counter = categories[`${i.category.toLowerCase()}Counter`])

console.log(items)

answered Aug 9, 2022 at 14:29

Nick

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Comments

Mrwaks · Accepted Answer · 2022-08-09 14:36:51Z

You can do this with the Array.forEach() method.

I advise you to do this with a regex, it avoids keyboard errors if your category ever comes in all lowercase or all uppercase, or even a mixture of the two, sometimes our fingers wander from typing code haha

let items = [
    {name: 'Carlsberg', category: 'Beer', price: '4.99'},
    {name: 'Smirnoff', category: 'Vodka', price: '28.99'},
    {name: 'Miller Lite', category: 'Beer', price: '7.99'}
 ]

const categories = {
    beerCounter: 2,
    vodkaCounter: 1,
};

items.forEach(item => {
    if (/^beer/i.test(item.category)) {
        item.counter = categories.beerCounter;
    }
    if (/^vodka/i.test(item?.category)) {
        item.counter = categories.vodkaCounter;
    }
});

console.log(items);

Good luck dude !

Timoteo Borgobello · Accepted Answer · 2022-08-09 14:50:34Z

1

let items = [
   {name: 'Carlsberg', category: 'Beer', price: '4.99'},
   {name: 'Smirnoff', category: 'Vodka', price: '28.99'},
   {name: 'Miller Lite', category: 'Beer', price: '7.99'}
]

items.forEach((item) => {
  if(item.category === 'Beer'){
  item.categories = categories.beerCounter
}
})

answered Aug 9, 2022 at 14:50

Timoteo Borgobello

112 bronze badges

1 Comment

Community Over a year ago

Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

Juan Trejos · Accepted Answer · 2022-08-09 17:18:42Z

0

You can use map or forEach

let items = [
   {name: 'Carlsberg', category: 'Beer', price: '4.99'},
   {name: 'Smirnoff', category: 'Vodka', price: '28.99'},
   {name: 'Miller Lite', category: 'Beer', price: '7.99'}
]

const categories = {
    beerCounter:2,
    vodkaCounter:1,
}

items.forEach(item=>{
  if(item.category === 'Beer')
    item.counter = categories.beerCounter;
  if(item.category === 'Vodka')
    item.counter = categories.vodkaCounter;
})

console.log(items);

edited Aug 9, 2022 at 17:18

answered Aug 9, 2022 at 14:31

Juan Trejos

1216 bronze badges

2 Comments

Jaromanda X Over a year ago

Why use .map of you throw away the array of undefineds you created for no reason at all?

Juan Trejos Over a year ago

It is preferable to use forEach, more than map if you we're not going to use the retourned values.

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