Compare two Arrays with Objects and create new array with unmatched objects - javascript

I have the following two Javascript arrays:
const array1 = [{ id: 1}, { id: 2 }, { id: 3 }, { id: 4}];
const array2 = [{ id: 1}, { id: 3 }];
I now want a new array array3 that contains only the objects that aren't already in array2, so:
const array3 = [{ id: 2}, { id: 4 }];
I have tried the following but it returns all objects, and when I changed the condition to === it returns the objects of array2.
const array3 = array1.filter(entry1 => {
return array2.some(entry2 => entry1.id !== entry2.id);
});
Any idea? ES6 welcome

You could reverse the comparison (equal instead of unqual) and return the negated result of some.
const
array1 = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }],
array2 = [{ id: 1 }, { id: 3 }],
array3 = array1.filter(entry1 => !array2.some(entry2 => entry1.id === entry2.id));
// ^ ^^^
console.log(array3);

Nina's answer is a good start but will miss any unique elements in array 2.
This extends her answer to get the unique elements from each array and then combine them:
const
array1 = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }],
array2 = [{ id: 1 }, { id: 3 }, { id: 5 }],
array3 = array1.filter(entry1 => !array2.some(entry2 => entry1.id === entry2.id)),
array4 = array2.filter(entry1 => !array1.some(entry2 => entry1.id === entry2.id)),
array5 = array3.concat(array4);
console.log(array5);

Related

How to get unique element from two arrays in js?

I'm trying to get unique (by id) values from two arrays.
But it returns whole array instead of { id: 3 }
const a = [{ id: 1 }, { id: 2 }];
const b = [{ id: 1 }, { id: 2 }, { id: 3 }];
const array3 = b.filter((obj) => a.indexOf(obj) == -1);
console.log(array3);
What's wrong here?
You cannot compare objects you should check that an element with that id doesn't exists in the other array
here I used some that returns a boolean if he can find a match
const a = [{
id: 1
}, {
id: 2
}];
const b = [{
id: 1
}, {
id: 2
}, {
id: 3
}];
const array3 = b.filter(obj => !a.some(({id}) => obj.id === id));
console.log(array3)
In your case, the following code gives all unique objects as an array, based on the id.
const a = [{
id: 1
}, {
id: 2
}];
const b = [{
id: 1
}, {
id: 2
}, {
id: 3
}];
const array3 = b.filter(objB => a.some((objA) => objB.id !== objA.id));
console.log(array3)
A different approach with a symmetrically result.
const
take = m => d => o => m.set(o.id, (m.get(o.id) || 0) + d),
a = [{ id: 1 }, { id: 2 }],
b = [{ id: 1 }, { id: 2 }, { id: 3 }],
map = new Map(),
add = take(map),
result = [];
a.forEach(add(1));
b.forEach(add(-1));
map.forEach((v, id) => v && result.push({ id }));
console.log(result);

Compare two arrays of objects, and remove if object value is equal

I've tried modifying some of the similar solutions on here but I keep getting stuck, I believe I have part of this figured out however, the main caveat is that:
Some of the objects have extra keys, which renders my object comparison logic useless.
I am trying to compare two arrays of objects. One array is the original array, and the other array contains the items I want deleted from the original array. However there's one extra issue in that the second array contains extra keys, so my comparison logic doesn't work.
An example would make this easier, let's say I have the following two arrays:
const originalArray = [{id: 1, name: "darnell"}, {id: 2, name: "funboi"},
{id: 3, name: "jackson5"}, {id: 4, name: "zelensky"}];
const itemsToBeRemoved = [{id: 2, name: "funboi", extraProperty: "something"},
{id: 4, name: "zelensky", extraProperty: "somethingelse"}];
after running the logic, my final output should be this array:
[{id: 1, name: "darnell"}, {id: 3, name: "jackson5"}]
And here's the current code / logic that I have, which compares but doesn't handle the extra keys. How should I handle this? Thank you in advance.
const prepareArray = (arr) => {
return arr.map((el) => {
if (typeof el === "object" && el !== null) {
return JSON.stringify(el);
} else {
return el;
}
});
};
const convertJSON = (arr) => {
return arr.map((el) => {
return JSON.parse(el);
});
};
const compareArrays = (arr1, arr2) => {
const currentArray = [...prepareArray(arr1)];
const deletedItems = [...prepareArray(arr2)];
const compared = currentArray.filter((el) => deletedItems.indexOf(el) === -1);
return convertJSON(compared);
};
How about using filter and some? You can extend the filter condition on select properties using &&.
const originalArray = [
{ id: 1, name: 'darnell' },
{ id: 2, name: 'funboi' },
{ id: 3, name: 'jackson5' },
{ id: 4, name: 'zelensky' },
];
const itemsToBeRemoved = [
{ id: 2, name: 'funboi', extraProperty: 'something' },
{ id: 4, name: 'zelensky', extraProperty: 'somethingelse' },
];
console.log(
originalArray.filter(item => !itemsToBeRemoved.some(itemToBeRemoved => itemToBeRemoved.id === item.id))
)
Or you can generalise it as well.
const originalArray = [
{ id: 1, name: 'darnell' },
{ id: 2, name: 'funboi' },
{ id: 3, name: 'jackson5' },
{ id: 4, name: 'zelensky' },
];
const itemsToBeRemoved = [
{ id: 2, name: 'funboi', extraProperty: 'something' },
{ id: 4, name: 'zelensky', extraProperty: 'somethingelse' },
];
function filterIfSubset(originalArray, itemsToBeRemoved) {
const filteredArray = [];
for (let i = 0; i < originalArray.length; i++) {
let isSubset = false;
for (let j = 0; j < itemsToBeRemoved.length; j++) {
// check if whole object is a subset of the object in itemsToBeRemoved
if (Object.keys(originalArray[i]).every(key => originalArray[i][key] === itemsToBeRemoved[j][key])) {
isSubset = true;
}
}
if (!isSubset) {
filteredArray.push(originalArray[i]);
}
}
return filteredArray;
}
console.log(filterIfSubset(originalArray, itemsToBeRemoved));
Another simpler variation of the second approach:
const originalArray = [
{ id: 1, name: 'darnell' },
{ id: 2, name: 'funboi' },
{ id: 3, name: 'jackson5' },
{ id: 4, name: 'zelensky' },
];
const itemsToBeRemoved = [
{ id: 2, name: 'funboi', extraProperty: 'something' },
{ id: 4, name: 'zelensky', extraProperty: 'somethingelse' },
];
const removeSubsetObjectsIfExists = (originalArray, itemsToBeRemoved) => {
return originalArray.filter(item => {
const isSubset = itemsToBeRemoved.some(itemToBeRemoved => {
return Object.keys(item).every(key => {
return item[key] === itemToBeRemoved[key];
});
});
return !isSubset;
});
}
console.log(removeSubsetObjectsIfExists(originalArray, itemsToBeRemoved));
The example below is a reusable function, the third parameter is the key to which you compare values from both arrays.
Details are commented in example
const arr=[{id:1,name:"darnell"},{id:2,name:"funboi"},{id:3,name:"jackson5"},{id:4,name:"zelensky"}],del=[{id:2,name:"funboi",extraProperty:"something"},{id:4,name:"zelensky",extraProperty:"somethingelse"}];
/** Compare arrayA vs. delArray by a given key's value.
--- ex. key = 'id'
**/
function deleteByKey(arrayA, delArray, key) {
/* Get an array of only the values of the given key from delArray
--- ex. delList = [1, 2, 3, 4]
*/
const delList = delArray.map(obj => obj[key]);
/* On every object of arrayA compare delList values vs
current object's key's value
--- ex. current obj[id] = 2
--- [1, 2, 3, 4].includes(obj[id])
Any match returns an empty array and non-matches are returned
in it's own array.
--- ex. ? [] : [obj]
The final return is a flattened array of the non-matching objects
*/
return arrayA.flatMap(obj => delList.includes(obj[key]) ? [] : [obj]);
};
console.log(deleteByKey(arr, del, 'id'));
let ff = [{ id: 1, name: 'darnell' }, { id: 2, name: 'funboi' },
{ id: 3, name: 'jackson5' },
{ id: 4, name: 'zelensky' }]
let cc = [{ id: 2, name: 'funboi', extraProperty: 'something' },
{ id: 4, name: 'zelensky', extraProperty: 'somethingelse' }]
let ar = []
let out = []
const result = ff.filter(function(i){
ar.push(i.id)
cc.forEach(function(k){
out.push(k.id)
})
if(!out.includes(i.id)){
// console.log(i.id, i)
return i
}
})
console.log(result)

I need to delete the object list by using matched key. (example the key have 1 and 2 , the result will only show 3)

let selectedRow = ["1","2","3"];
let arr = [
{ id:1, name:"eddie" },
{ id:2, name:"jake" },
{ id:3, name:"susan" },
];
Updation on the answer provided by Andy, If you don't want to update the exiting array and want to result in a new array
let selectedRow = ["1", "2"];
let arr = [
{ id: 1, name: "eddie" },
{ id: 2, name: "jake" },
{ id: 3, name: "susan" },
];
const result = arr.filter(item => !selectedRow.includes(item.id.toString()))
console.log(result)
If you want changes in a current array and don't want to store results in a new array (Not the most efficient solution though)
let selectedRow = ["1", "2"];
let arr = [
{ id: 1, name: "eddie" },
{ id: 2, name: "jake" },
{ id: 3, name: "susan" },
];
for (const row of selectedRow) {
const index = arr.findIndex(item => item.id.toString() === row)
if (index !== -1)
arr.splice(index, 1)
}
console.log(arr)
Make sure your selectedRow array is an array of numbers (because your object ids are numbers).
filter over the array of objects and only keep the ones that selectedRow doesn't include.
const arr = [{ id: 1, name: 'eddie' }, { id: 2, name: 'jake' }, { id: 3, name: 'susan' }];
const selectedRow = ['1', '2'].map(Number);
const result = arr.filter(obj => {
return !selectedRow.includes(obj.id);
});
console.log(result);

filter array of object using an array [duplicate]

This question already has an answer here:
Filter array of object from another array
(1 answer)
Closed 3 years ago.
I want to filter an array of objects using an array but I want the results on the basis of array index and the result should be repeated when the array index value is repeated.
const data = [{
id='1',
name:'x'
},
{
id='4',
name:'a'
},
{
id='2',
name:'y'
},
{
id='3',
name:'z'
}
]
cons idArray = [1,4,3,2,4,3,2]
I have tried following code and get the result only once
const filteredData = data.filter(arrayofObj => idArray.includes(arrayofObj.id))
console.log(filteredData)
expected output is
expected output is =
[{id = '1,name:'x'},{id='4',name:'a'},{
id='3',
name:'z'
},
{
id='2',
name:'y'
},{
id='4',
name:'a'
},
{
id='3',
name:'z'
},{
id='2',
name:'y'
}]
First convert data array into Object with id's as keys.
Second, use map method over idArray and gather objects from above object.
const data = [
{
id: "1",
name: "x"
},
{
id: "4",
name: "a"
},
{
id: "2",
name: "y"
},
{
id: "3",
name: "z"
}
];
const dataObj = data.reduce((acc, curr) => {
acc[curr.id] = { ...curr };
return acc;
}, {});
const idArray = [1, 4, 3, 2, 4, 3, 2];
const results = idArray.map(id => ({ ...dataObj[id] }));
console.log(results);
You could map with a Map.
const
data = [{ id: '1', name: 'x' }, { id: '4', name: 'a' }, { id: '2', name: 'y' }, { id: '3', name: 'z' }],
idArray = [1, 4, 3, 2, 4, 3, 2],
result = idArray.map(Map.prototype.get, new Map(data.map(o => [+o.id, o])));
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

If you want to remove an object from the first array which is not present in second array

If you want to remove more than one object from the first array "arrayOne" which is not present in the second array "arrayTwo". It's just a suggestion the way I do. If you have any other way please let me know.
let arrayOne = [{
id: 1
}, {
id: 2
}, {
id: 3
}]
let arrayTwo = [{
id: 2
},{
id: 3
}]
for (var index = arrayOne.length; index--;) {
if (!arrayTwo.find(y => y.id === arrayOne[index].id)) {
arrayOne.splice(arrayOne.findIndex(z => z.id === arrayOne[index].id), 1)
console.log("After splice", arrayOne)
}
You can also use a Set to store ids of elements of arrayTwo and then filter to extract only those elements of arrayOne that are also present in arrayTwo:
let arrayOne = [{
id: 1
}, {
id: 2
}, {
id: 3
}];
let arrayTwo = [{
id: 2
}];
let arrayTwoSet = new Set(arrayTwo.map(e => e.id));
console.log(arrayOne.filter(e => arrayTwoSet.has(e.id)));
use Array.some() inside Array.filter()
let arrayOne = [{ id: 1 }, { id: 2 }, { id: 3 }] ;
let arrayTwo = [{ id: 2 }];
const result = arrayOne.filter(obj1 => !arrayTwo.some(obj2 => obj1.id === obj2.id));
console.log('final array : ', result);

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