Having trouble with filtering an array using the some() method of another array?

Question

Having trouble with filtering an array using the some() method of another array?

When utilizing the code below, my goal is to filter the first array by checking if the item's id exists in the second array. However, I am encountering an issue where the result is coming back empty.

dialogRef.afterClosed().subscribe((airlines: AirlineModel[]) => {
    console.log(airlines, this.airlines);
    const updates = airlines.filter(airline => this.airlines.some(item => item.id === airline.id));
    console.log(updates);
});

The output of

console.log(airlines, this.airlines);

shows:

(13) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
0: {id: "1", code: "AAL", name: "American Airlines"}
1: {id: "6", code: "DAL", name: "Delta Airlines"}
2: {id: "526", code: "SWA", name: "Southwest Airlines"}
3: {id: "27", code: "ASA", name: "Alaska Airlines"}
4: {id: "23", code: "FDX", name: "FedEx"}
5: {id: "205", code: "NCA", name: "Nippon Cargo"}
6: {id: "406", code: "UPS", name: "United Parcel Service"}
7: {id: "160", code: "CPA", name: "Cathay Pacific"}
8: {id: "403", code: "PAC", name: "Polar Air Cargo"}
9: {id: "992", code: "GTI", name: "Atlas Air"}
10: {id: "272", code: "CKS", name: "Kalitta Air"}
11: {id: "345", code: "NAC", name: "Northern Air Cargo"}
12: {id: "615", code: "BCS", name: "European Air Transport"}
length: 13
__proto__: Array(0)

(12) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
0: {id: 6, code: "DAL", name: "Delta Airlines"}
1: {id: 526, code: "SWA", name: "Southwest Airlines"}
2: {id: 27, code: "ASA", name: "Alaska Airlines"}
3: {id: 23, code: "FDX", name: "FedEx"}
4: {id: 205, code: "NCA", name: "Nippon Cargo"}
5: {id: 406, code: "UPS", name: "United Parcel Service"}
6: {id: 160, code: "CPA", name: "Cathay Pacific"}
7: {id: 403, code: "PAC", name: "Polar Air Cargo"}
8: {id: 992, code: "GTI", name: "Atlas Air"}
9: {id: 272, code: "CKS", name: "Kalitta Air"}
10: {id: 345, code: "NAC", name: "Northern Air Cargo"}
11: {id: 615, code: "BCS", name: "European Air Transport"}
length: 12
__proto__: Array(0)

The result of console.log(updates); appears as:

[]length: 0__proto__: Array(0)

javascript angular typescript ecmascript-6

Answer 1

Answer №1

The car manufacturers id attribute is a string, whereas the this.carManufacturers id attribute is a number. To accommodate this difference in data types, it is recommended to switch from using the strict equality operator === to the abstract equality operator ==.

For more information on equality comparisons and sameness, refer to the following link: Equality comparisons and sameness on mdn.

const carManufacturers = [{"id":"1","name":"Toyota"},{"id":"2","name":"Honda"},{"id":"3","name":"Ford"},{"id":"4","name":"Chevrolet"}];

const thisCarManufacturers = [{"id":2,"name":"Honda"},{"id":3,"name":"Ford"},{"id":5,"name":"Tesla"}];

const updates = carManufacturers.filter(manufacturer => 
  thisCarManufacturers.some(item => item.id == manufacturer.id)
);

console.log(updates);

Instead of relying solely on abstract equality, you have the option to convert the string id to a number by using the unary plus operator +, as demonstrated in +carManufacturers.id. Conversely, you can convert the number to a string by utilizing String(this.carManufacturers.id).

const carManufacturers = [{"id":"1","name":"Toyota"},{"id":"2","name":"Honda"},{"id":"3","name":"Ford"},{"id":"4","name":"Chevrolet"}];

const thisCarManufacturers = [{"id":2,"name":"Honda"},{"id":3,"name":"Ford"},{"id":5,"name":"Tesla"}];

const updates = carManufacturers.filter(manufacturer => 
  thisCarManufacturers.some(item => item.id === +manufacturer.id)
);

console.log(updates);

If you are working with TypeScript and performing this comparison multiple times, it would be beneficial to create a Set containing the string ids of this.carManufacturers for efficient comparison:

const carManufacturers = [{"id":"1","name":"Toyota"},{"id":"2","name":"Honda"},{"id":"3","name":"Ford"},{"id":"4","name":"Chevrolet"}];

const thisCarManufacturers = [{"id":2,"name":"Honda"},{"id":3,"name":"Ford"},{"id":5,"name":"Tesla"}];

const thisCarManufacturersSet = thisCarManufacturers.reduce((s, o) => s.add(String(o.id)), new Set);

const updates = carManufacturers.filter(manufacturer => 
  thisCarManufacturersSet.has(manufacturer.id)
);

console.log(updates);

Answer 2

The car manufacturers id attribute is a string, whereas the this.carManufacturers id attribute is a number. To accommodate this difference in data types, it is recommended to switch from using the strict equality operator === to the abstract equality operator ==.

For more information on equality comparisons and sameness, refer to the following link: Equality comparisons and sameness on mdn.

const carManufacturers = [{"id":"1","name":"Toyota"},{"id":"2","name":"Honda"},{"id":"3","name":"Ford"},{"id":"4","name":"Chevrolet"}];

const thisCarManufacturers = [{"id":2,"name":"Honda"},{"id":3,"name":"Ford"},{"id":5,"name":"Tesla"}];

const updates = carManufacturers.filter(manufacturer => 
  thisCarManufacturers.some(item => item.id == manufacturer.id)
);

console.log(updates);

Instead of relying solely on abstract equality, you have the option to convert the string id to a number by using the unary plus operator +, as demonstrated in +carManufacturers.id. Conversely, you can convert the number to a string by utilizing String(this.carManufacturers.id).

const carManufacturers = [{"id":"1","name":"Toyota"},{"id":"2","name":"Honda"},{"id":"3","name":"Ford"},{"id":"4","name":"Chevrolet"}];

const thisCarManufacturers = [{"id":2,"name":"Honda"},{"id":3,"name":"Ford"},{"id":5,"name":"Tesla"}];

const updates = carManufacturers.filter(manufacturer => 
  thisCarManufacturers.some(item => item.id === +manufacturer.id)
);

console.log(updates);

If you are working with TypeScript and performing this comparison multiple times, it would be beneficial to create a Set containing the string ids of this.carManufacturers for efficient comparison:

const carManufacturers = [{"id":"1","name":"Toyota"},{"id":"2","name":"Honda"},{"id":"3","name":"Ford"},{"id":"4","name":"Chevrolet"}];

const thisCarManufacturers = [{"id":2,"name":"Honda"},{"id":3,"name":"Ford"},{"id":5,"name":"Tesla"}];

const thisCarManufacturersSet = thisCarManufacturers.reduce((s, o) => s.add(String(o.id)), new Set);

const updates = carManufacturers.filter(manufacturer => 
  thisCarManufacturersSet.has(manufacturer.id)
);

console.log(updates);

Answer 3

Answer №2

The issue arises from the filter method using the === operator, which also considers variable types during comparison. In this case, the arrays have different id types - this.airlines uses ids of type number while airlines uses ids of type string. By replacing the === operator with ==, the problem should be resolved.

Answer 4

The issue arises from the filter method using the === operator, which also considers variable types during comparison. In this case, the arrays have different id types - this.airlines uses ids of type number while airlines uses ids of type string. By replacing the === operator with ==, the problem should be resolved.

Answer 5

Answer №3

To ensure accurate comparison, it is important to use the correct operator. Instead of using "===", you can use "==" in this scenario to correctly compare the types.

Answer 6

To ensure accurate comparison, it is important to use the correct operator. Instead of using "===", you can use "==" in this scenario to correctly compare the types.

Answer 7

Answer №4

 let updatedAirlines = airlines.filter(airline => this.airlines.some(item => +item.id === +airline.id));

Ensure type safety by using ===, and make sure to convert values to integers for safe comparison.

Answer 8

 let updatedAirlines = airlines.filter(airline => this.airlines.some(item => +item.id === +airline.id));

Ensure type safety by using ===, and make sure to convert values to integers for safe comparison.

Having trouble with filtering an array using the some() method of another array?

Answer №1

Answer №2

Answer №3

Answer №4

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