Filtering an array by eliminating items stored in other arrays at corresponding indexes that were also removed

Question

Filtering an array by eliminating items stored in other arrays at corresponding indexes that were also removed

I need to filter out specific items from an array (testCopy) while also removing the corresponding items in other arrays (testCopy2 and testCopy3). For example, I want the filtered result to be testCopy [0, 2], testCopy2 [1,3], and testCopy3 [3,5]. Essentially, I want to remove the same items from the other two arrays that were removed from the index being filtered. I attempted to slice them off by using the filter but it didn't work as expected. Do you have any suggestions on how to achieve this?

let test = [0, 1, 2, 4, 5];
let test2 = [1, 2, 3, 6, 5];
let test3 = [3, 4, 5, 8, 9];

let testCopy = [...test];
let testCopy2 = [...test2];
let testCopy3 = [...test3];

let testClone = testCopy.filter((item, index) => {
  if (item === 0 || item === 2) {
    return true;
  } else {
    testCopy2.splice(index, 1);
    testCopy3.splice(index, 1);
    return false
  }
});

console.log(testClone, testCopy2, testCopy3); // [0, 2],  [1, 3, 6], [3, 5, 8]

javascript arrays

Answer 1

Answer №1

If you wish to skip the initialization of testCopy2 and testCopy3, here is an alternative approach:

let test = [0, 1, 2, 4, 5];
let test2 = [1, 2, 3, 6, 5];
let test3 = [3, 4, 5, 8, 9];

let testCopy = [...test];
let testCopy2 = [];
let testCopy3 = [];

let testClone = testCopy.filter((item, index) => {
  if (item === 0 || item === 2) {
    testCopy2.push(test2[index]);
    testCopy3.push(test3[index]);
    return true;
  } else {
    return false;
  }
});

console.log(testClone, testCopy2, testCopy3);

Answer 2

If you wish to skip the initialization of testCopy2 and testCopy3, here is an alternative approach:

let test = [0, 1, 2, 4, 5];
let test2 = [1, 2, 3, 6, 5];
let test3 = [3, 4, 5, 8, 9];

let testCopy = [...test];
let testCopy2 = [];
let testCopy3 = [];

let testClone = testCopy.filter((item, index) => {
  if (item === 0 || item === 2) {
    testCopy2.push(test2[index]);
    testCopy3.push(test3[index]);
    return true;
  } else {
    return false;
  }
});

console.log(testClone, testCopy2, testCopy3);

Answer 3

Answer №2

If you want to inject a null using splice and then filter them out, keep in mind that it may involve multiple loops.

const test = [0,1,2,4,5];
const test2 = [1,2,3,6,5];
const test3 = [3,4,5,8,9];

const testCopy = [...test];
const testCopy2 = [...test2];
const testCopy3 = [...test3];

const testClone = testCopy.filter((item,index)=>{
    if(item === 0 || item === 2) { 
        return true;
    } else { 
        testCopy2.splice(index,1,null);
        testCopy3.splice(index,1,null);
        return false
    }
});

testCopy2 = testCopy2.filter((val) => val !== null)
testCopy3 = testCopy3.filter((val) => val !== null)

Answer 4

If you want to inject a null using splice and then filter them out, keep in mind that it may involve multiple loops.

const test = [0,1,2,4,5];
const test2 = [1,2,3,6,5];
const test3 = [3,4,5,8,9];

const testCopy = [...test];
const testCopy2 = [...test2];
const testCopy3 = [...test3];

const testClone = testCopy.filter((item,index)=>{
    if(item === 0 || item === 2) { 
        return true;
    } else { 
        testCopy2.splice(index,1,null);
        testCopy3.splice(index,1,null);
        return false
    }
});

testCopy2 = testCopy2.filter((val) => val !== null)
testCopy3 = testCopy3.filter((val) => val !== null)

Answer 5

Answer №3

Generate a list of specific items to retain by using the method Array.map() on the initial array, and deciding whether to return true or false based on set criteria. Proceed to filter all arrays using the corresponding index from the collection of items to keep.

const test = [0,1,2,4,5];
const test2 = [1,2,3,6,5];
const test3 = [3,4,5,8,9];

const keepItems = test.map(item => item === 0 || item === 2)
const testCopy = test.filter((_, i) => keepItems[i]);
const testCopy2 = test2.filter((_, i) => keepItems[i]);
const testCopy3 = test3.filter((_, i) => keepItems[i]);

console.log(testCopy, testCopy2, testCopy3); // [0, 2],  [1, 3], [3, 5]

Answer 6

Generate a list of specific items to retain by using the method Array.map() on the initial array, and deciding whether to return true or false based on set criteria. Proceed to filter all arrays using the corresponding index from the collection of items to keep.

const test = [0,1,2,4,5];
const test2 = [1,2,3,6,5];
const test3 = [3,4,5,8,9];

const keepItems = test.map(item => item === 0 || item === 2)
const testCopy = test.filter((_, i) => keepItems[i]);
const testCopy2 = test2.filter((_, i) => keepItems[i]);
const testCopy3 = test3.filter((_, i) => keepItems[i]);

console.log(testCopy, testCopy2, testCopy3); // [0, 2],  [1, 3], [3, 5]

Answer 7

Answer №4

Using splice() to delete array elements directly affects the positions of other elements, causing unexpected output due to shifted indices.

When splice() removes an element from an array, only elements that come after the deleted one are impacted, not those preceding it.

To prevent index conflicts resulting from in-place deletion, a solution is to iterate over the array in reverse order and perform the deletions accordingly.

let test = [0,1,2,4,5];
let test2 = [1,2,3,6,5];
let test3 = [3,4,5,8,9];

let testCopy = [...test];
let testCopy2 = [...test2];
let testCopy3 = [...test3];

for (let i = testCopy.length - 1; i >= 0; i--) {
  if(testCopy[i] !== 0 && testCopy[i] !== 2) { 
    testCopy.splice(i, 1);
    testCopy2.splice(i, 1);
    testCopy3.splice(i, 1);
  }
}

console.log(testCopy, testCopy2, testCopy3);

Answer 8

Using splice() to delete array elements directly affects the positions of other elements, causing unexpected output due to shifted indices.

When splice() removes an element from an array, only elements that come after the deleted one are impacted, not those preceding it.

To prevent index conflicts resulting from in-place deletion, a solution is to iterate over the array in reverse order and perform the deletions accordingly.

let test = [0,1,2,4,5];
let test2 = [1,2,3,6,5];
let test3 = [3,4,5,8,9];

let testCopy = [...test];
let testCopy2 = [...test2];
let testCopy3 = [...test3];

for (let i = testCopy.length - 1; i >= 0; i--) {
  if(testCopy[i] !== 0 && testCopy[i] !== 2) { 
    testCopy.splice(i, 1);
    testCopy2.splice(i, 1);
    testCopy3.splice(i, 1);
  }
}

console.log(testCopy, testCopy2, testCopy3);

Filtering an array by eliminating items stored in other arrays at corresponding indexes that were also removed

Answer №1

Answer №2

Answer №3

Answer №4

Similar questions

The issue of Segmentation fault in C programming when using an array inside a

Camera Capacitor designed to eliminate popup notifications

Guide on properly accessing a properties file in JavaScript within the project directory?

The array in Objective C threw an NSRangeException when attempting to access index 11, which is beyond the bounds of

Looking to display an alert message upon scrolling down a specific division element in HTML

Escape from the chains of node.js then() statements

Encountering a no-loops/no-loops eslint error in node.js code while attempting to utilize the for and for-of loops

Node.js is unable to handle the contents of an SNS event message

What steps do I need to take to develop a CLI application similar to ng, that can be installed globally on the system

The parameters used in the json.parse function in javascript may be difficult to interpret

The courier stranded in the process of sending a request - express js mongodb

Implementing the linking of a URL to an HTML hidden button that is dynamically displayed through a Javascript program

Wildcard whitelisting in middleware systems

Isolating an array from an object?

Code needed for blocking screens in Javascript/AJAX

Issue with jQuery tooltip not showing information when there is a space present

Angular can help you easily convert numbers into a money format

Challenges with displaying TreeTable in SAPUI5

Uib-tabset - update triggered by successful HTTP response

Utilizing Conditional Styling for an Array of Objects within a Textarea in Angular 6