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I'm trying to find and replace the array if an incoming arrays matches the existing one but unfortunately, I'm stucked with the some

Here's my existing array.

let existingData = [{
    id: 1,
    product: 'Soap',
    price: '$2'
},{
    id: 2,
    product: 'Sofa',
    price: '$30'
},{
    id: 3,
    product: 'Chair',
    price: '$45'
}]

And here's my incoming array.

const updateData = [{
    id: 1,
    product: 'Soap',
    price: '$3'
},{
    id: 2,
    product: 'Sofa',
    price: '$35'
}]

So far, I saw the foreach but unfortunately, I'm not sure how can I use it if the term is an array. But I get stuck and I can't proceed.

const updateData = [{
    id: 1,
    product: 'Soap',
    price: '$3'
},{
    id: 2,
    product: 'Sofa',
    price: '$35'
}]

existingData.forEach(d=>{
    if(d.id === ??? how can I match this to the incoming array?)
    // if matches, then update the existing data with the updated one.
})

And the expected result must be something like this:

let existingData = [{
    id: 1,
    product: 'Soap',
    price: '$3'
},{
    id: 2,
    product: 'Sofa',
    price: '$35'
},{
    id: 3,
    product: 'Chair',
    price: '$45'
}]

If in some cases, the data is not present in the existingData, then the incoming array will just add simply in the existing array.

Please help how can I achieve it and if there's a better and cleaner way to do this, please let me know. Thank you!

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1
  • 1
    what is your expected result? Commented May 31, 2021 at 11:45

3 Answers 3

Reset to default
1

You can easily achieve this result using forEach and find

let existingData = [{
    id: 1,
    product: "Soap",
    price: "$2",
  },
  {
    id: 2,
    product: "Sofa",
    price: "$30",
  },
  {
    id: 3,
    product: "Chair",
    price: "$45",
  },
];

const updateData = [{
    id: 1,
    product: "Soap",
    price: "$3",
  },
  {
    id: 2,
    product: "Sofa",
    price: "$35",
  },
];

updateData.forEach((obj) => {
  let isExist = existingData.find((o) => o.id === obj.id);
  if (isExist) {
    isExist.price = obj.price;
    isExist.product = obj.product;
  }
});

console.log(existingData);

If there are multiple properties that need to be updated then you can use for..in loop over the updated object and replace the prop in the existing property.

updateData.forEach((obj) => {
  let isExist = existingData.find((o) => o.id === obj.id);
  if (isExist) {
    for (let prop in obj) {
      isExist[prop] = obj[prop];
    }
  }
});

If you want to add the data if it doesn't exist in the existing array then you need to push it into existingData array.

let existingData = [{
    id: 1,
    product: "Soap",
    price: "$2",
  },
  {
    id: 2,
    product: "Sofa",
    price: "$30",
  },
  {
    id: 3,
    product: "Chair",
    price: "$45",
  },
];

const updateData = [{
    id: 1,
    product: "Soap",
    price: "$3",
  },
  {
    id: 2,
    product: "Sofa",
    price: "$35",
  },
  {
    id: 6,
    product: "Sofa",
    price: "$135",
  },
];

updateData.forEach((obj) => {
  let isExist = existingData.find((o) => o.id === obj.id);
  if (isExist) {
    for (let prop in obj) {
      isExist[prop] = obj[prop];
    }
  } else {
    existingData.push(obj);
  }
});

console.log(existingData);

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4 Comments

What if I have a new array that doesn't match the existing data and I only want to insert it? how can I achieve it?
Do you want to add the element at the sorting order. or at the end
The sorting isn't important though :)) But correct me if I'm wrong, so basically, I'll just add else after the isExist block to add it if it's not yet exists. Am I correct?
Check it out @JokerBench
1 
existingData.forEach(existingItem => {
 let item = updatedDate.find(u => u.id === existingItem.id);
 if(item){
    existingItem.product = item.product;
    existingItem.price= item.price;
  }
});
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Comments

1

Given your existingData and updateData, you can quite simply do something like this:

// form a temporary object mapping updated objects' ids to the new ids
const updateDataByKeys = Object.fromEntries(updateData.map(e => [e.id, e]));

// map through `existingData`, replacing old entries with updated where they
// exist in the above temporary object, using the old object if they don't.
const newData = existingData.map(e => updateDataByKeys[e.id] || e);

Creating the temporary object should make this approach quite a bit faster than approaches using .find() on updateData.

If you need to merge the data from updateData into the existing objects, you could do

const newData = existingData.map(
  e => updateDataByKeys[e.id] ? ({...e, ...updateDataByKeys[e.id]}) : e
);

EDIT: Based on comments, if you also need to add new objects from updateData:


// form a temporary object mapping updated objects' ids to the new ids
const updateDataByKeys = Object.fromEntries(updateData.map(e => [e.id, e]));

// Map through `existingData`, replacing old entries with updated where they
// exist in the above temporary object, using the old object if they don't.
// When using an update object, removes it from the mapping; the left-over
// new data (which had no ID in the old data) are then concatenated to the
// list.
const newData = existingData.map(e => {
    if(updateDataByKeys[e.id]) {
        const val = updateDataByKeys[e.id];
        delete updateDataByKeys[e.id];
        return val;
    }
    return e;
}).concat(Object.values(updateDataByKeys));
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1 Comment

HI @AKX but what if the incoming data has no matching existing data by id, then what I need also is that it will add automatically to the existing data array.

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