How to reorder a JavaScript array according to a specific order from another array?

Other Questions JavaScript
1

I’m trying to find a way to rearrange an array based on the order specified in another array. For instance, I have the following data structure:

elements = [
    ['Alice', 'x'],
    ['Charlie', 'y'],
    ['Eve', 'y'],
    ['Mallory', 'z'],
    ['Oscar', 'w'],
    ['Trent', 'y']
]

And I want to sort it according to this reference:

orderPattern = ['y', 'w', 'y', 'y', 'x', 'z']

I don’t have unique identifiers to help with matching, and my goal is to reorder elements closely following orderPattern. The desired output should look like this:

elements = [
    ['Charlie', 'y'],
    ['Trent', 'y'],
    ['Eve', 'y'],
    ['Oscar', 'w'],
    ['Alice', 'x'],
    ['Mallory', 'z']
]

What would be the best way to achieve this?

2

To reorder a JavaScript array according to a specific order defined by another array, you can efficiently use the Array.prototype.sort() method. Here’s a straightforward approach:

const orderArray = ['b', 'c', 'a']; // Desired order
const originalArray = ['a', 'b', 'c', 'd', 'e'];

// Create a map with the desired order and sort the array based on this order
const orderMap = new Map(orderArray.map((item, index) => [item, index]));

const sortedArray = originalArray.sort((a, b) => {
  // Non-existing elements in orderArray will be placed at the end
  return (orderMap.get(a) ?? Infinity) - (orderMap.get(b) ?? Infinity);
});

console.log(sortedArray);
// Output: ['b', 'c', 'a', 'd', 'e']

Explanation:

  • We create a Map from the orderArray to store the index positions of each element for quick lookup.
  • Use Array.prototype.sort() to rearrange the originalArray by comparing indices of its elements from the map.
  • Elements not present in the orderArray are sorted to the end, but you can tweak this as needed.

This method is efficient and keeps the solution concise, optimizing the reordering process.

3

To reorder a JavaScript array based on the specific order defined in another array, you can utilize the array’s sort method with a custom comparator function. This function should use the indices from the ordering array to determine the new order of elements.

Consider the following example:

const originalArray = ['apple', 'banana', 'cherry', 'date'];
const orderArray = ['cherry', 'date', 'banana', 'apple'];

// Create an order map from the order array
const orderMap = new Map();
orderArray.forEach((item, index) => {
  orderMap.set(item, index);
});

// Sort the original array based on the order map
const reorderedArray = originalArray.sort((a, b) => {
  return orderMap.get(a) - orderMap.get(b);
});

console.log(reorderedArray); // ['cherry', 'date', 'banana', 'apple']

Explanation

  • Step 1: Create a map (orderMap) from the orderArray which associates each element with its index, allowing for quick lookups.
  • Step 2: Use the sort method on the originalArray, with a comparator that rearranges the elements based on their indices from orderMap.

This approach is efficient and well-suited for scenarios where you need to reorder arrays dynamically based on external configurations or inputs.

4

You can achieve this using map and indexOf. Here’s a quick way to reorder an array:

const order = ['b', 'c', 'a'];
const array = ['a', 'b', 'c'];

const reorderedArray = order.map(item => array[array.indexOf(item)]);
console.log(reorderedArray); // Output: ['b', 'c', 'a']

This snippet reorders array according to order.

5

Reordering a JavaScript array based on another array can be efficiently achieved using map and indexOf methods. Here’s a practical way to do it:

// Original array
const originalArray = ['apple', 'banana', 'cherry', 'date'];

// Order array
const orderArray = ['cherry', 'apple', 'date', 'banana'];

// Reordering the original array
const reorderedArray = orderArray.map(item => {
  return originalArray[originalArray.indexOf(item)];
});

console.log(reorderedArray); 
// Output: ['cherry', 'apple', 'date', 'banana']

Steps:

  1. Use map on your orderArray to iterate through its elements.
  2. Within each iteration, locate the current item in originalArray using indexOf.
  3. Return the item from originalArray based on the index found by indexOf.

Using this method ensures you efficiently reorder the array with minimal steps, enhancing code readability and execution speed.

6

If you want to reorder an array in JavaScript according to a specific order defined by another array, you can do so using a combination of map and indexOf methods. Here’s a practical and efficient approach:

Example

Suppose you have the following arrays:

const originalArray = ['apple', 'banana', 'cherry', 'date'];
const orderArray = ['banana', 'apple', 'date', 'cherry'];

You can reorder originalArray to match the order specified in orderArray like this:

const reorderedArray = orderArray.map(item => {
  return originalArray.find(element => element === item);
});

console.log(reorderedArray);
// Output: ['banana', 'apple', 'date', 'cherry']

Explanation

  • map(): Iterates over each element in orderArray.
  • find(): Looks for the matching element in originalArray.
  • The result is a new array ordered as specified by orderArray.

This approach ensures that the originalArray is reordered based on the specific sequence provided by orderArray, saving you time and effort with efficient and direct code.