Filter an object of array with another object of array

Question

I'm trying to filter an object of array localcartArr to exclude any object that's included in the products array, but it returns the same localcartArr without excluding this object:

{ "productID": "5f6fd57f8b6f6b0017992443" }

Which exists in products array, it works only with === operator, but doesn't work with the not equal operation != or !==.

const products = [
  {
    "_id": "60242abc209cbd32d8e85ec8",
    "productID": "5f6fd4f18b6f6b001799243f",
    "quantity": 2
  },
  {
    "_id": "60242b00209cbd32d8e85ec9",
    "productID": "5f6fd57f8b6f6b0017992443",
    "quantity": 1
  }
]
        
let localcartArr = [
  {                
    "productID": "5f6fd57f8b6f6b0017992443",
    "quantity": 2
  },
  {                   
    "productID": "5f6fd12a8b6f6b001799242f",
    "quantity": 1
  },
  {               
    "productID": "5f7a5668a9baa50017d495e8",
    "quantity": 1
  }
]

let filterd = localcartArr.filter(local => {
  return products.some(product => {
    return local.productID !==  product.productID    
  });
});

Does this answer your question? filter array of objects by another array of objects — evolutionxbox
– evolutionxbox, Commented Feb 10, 2021 at 21:09

Mr. Polywhirl · Accepted Answer · 2021-02-10 21:28:16Z

In order to invert "some / equal", you need to return "not every / not equal".

This is a principle of De Morgan's laws in boolean logic.

const products = [{
  "_id": "60242abc209cbd32d8e85ec8",
  "productID": "5f6fd4f18b6f6b001799243f",
  "quantity": 2
}, {
  "_id": "60242b00209cbd32d8e85ec9",
  "productID": "5f6fd57f8b6f6b0017992443",
  "quantity": 1
}];

const localcartArr = [
  { "productID": "5f6fd57f8b6f6b0017992443", "quantity": 2 },
  { "productID": "5f6fd12a8b6f6b001799242f", "quantity": 1 },
  { "productID": "5f7a5668a9baa50017d495e8", "quantity": 1 }
];

let filtered1 = localcartArr.filter(local =>
  products.some(product =>
    local.productID === product.productID));
    
let filtered2 = localcartArr.filter(local =>
  !products.every(product =>
    local.productID !== product.productID));

console.log(filtered1);
console.log(filtered2);

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Here is the same program, but simplified:

const products = [{
  "_id": "60242abc209cbd32d8e85ec8",
  "productID": "5f6fd4f18b6f6b001799243f",
  "quantity": 2
}, {
  "_id": "60242b00209cbd32d8e85ec9",
  "productID": "5f6fd57f8b6f6b0017992443",
  "quantity": 1
}];

const cart = [
  { "productID": "5f6fd57f8b6f6b0017992443", "quantity": 2 },
  { "productID": "5f6fd12a8b6f6b001799242f", "quantity": 1 },
  { "productID": "5f7a5668a9baa50017d495e8", "quantity": 1 }
];

const filterEqual = (a, b, c) => a.filter(x => b.some(y => (c(x) === c(y))));
const filterNotEqual = (a, b, c) => a.filter(x => !b.every(y => (c(x) !== c(y))));

const filtered1 = filterEqual(cart, products, ({productID}) => productID);
const filtered2 = filterNotEqual(cart, products, ({productID}) => productID);

console.log(filtered1);
console.log(filtered2);

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Mark Schultheiss · Accepted Answer · 2021-02-10 21:58:18Z

Filter using the property you want to match on and exclude that not matching.

Some examples:

const products = [{
    "_id": "60242abc209cbd32d8e85ec8",
    "productID": "5f6fd4f18b6f6b001799243f",
    "quantity": 2
  },
  {
    "_id": "60242b00209cbd32d8e85ec9",
    "productID": "5f6fd57f8b6f6b0017992443",
    "quantity": 1
  }
];

let localcartArr = [{
    "productID": "5f6fd57f8b6f6b0017992443",
    "quantity": 2
  },
  {
    "productID": "5f6fd12a8b6f6b001799242f",
    "quantity": 1
  },
  {
    "productID": "5f7a5668a9baa50017d495e8",
    "quantity": 1
  }
];
// find matches
const myArrayFiltered = localcartArr.filter((el) => {
  return products.some((f) => {
    return f.productID === el.productID;
  });
});

console.log(myArrayFiltered);

//filter out matches
const notIn = localcartArr.filter((el) => {
  return myArrayFiltered.some((f) => {
    return f.productID !== el.productID;
  });
});

console.log(notIn);

// to put it together (for clarity)
// not that this is not super efficient if you have a large pair of sets
const notInX = localcartArr.filter((el) => {
  return  localcartArr.filter((el) => {
  return products.some((f) => {
    return f.productID === el.productID;
  });
}).some((f) => {
    return f.productID !== el.productID;
  });
});
console.log(notInX);

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