5 Ways to Sort JS Arrays Using New Index from Another Array

JavaScript arrays are incredibly versatile, but sometimes you need to sort one array based on the order of another. This can be tricky, especially when the two arrays have different structures or content. Here are five effective methods to achieve this, each with its own strengths and use cases: 1. The Index Mapping Approach: Precision with map and indexOf

This method leverages the power of map and indexOf to create a direct mapping between elements in the sorting array and their indices. * When to Use: Ideal when you have a clear one-to-one correspondence between elements in both arrays and need precise control over the order. * How it Works:

   const sortingArray = ['c', 'a', 'b'];
   const targetArray = ['b', 'c', 'a'];

   const sortedArray = targetArray.map(element => {
     const index = sortingArray.indexOf(element);
     return { element, index };
   })
   .sort((a, b) => a.index - b.index)
   .map(item => item.element);

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

• We first create an array of objects, each containing the element from targetArray and its corresponding index in sortingArray.
• Then, we sort this array based on the index property.
• Finally, we extract the sorted elements using another map.

2. The Object Lookup Method: Efficiency with Key-Value Pairs

This approach uses an object to store the indices of the sorting array, allowing for efficient lookups. * When to Use: Suitable when the sorting array is relatively small and you want a more concise solution. * How it Works:

   const sortingArray = ['c', 'a', 'b'];
   const targetArray = ['b', 'c', 'a'];

   const indexMap = {};
   sortingArray.forEach((element, index) => {
     indexMap[element] = index;
   });

   const sortedArray = targetArray.slice().sort((a, b) => indexMap[a] - indexMap[b]);

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

• We create an object indexMap where keys are elements from sortingArray and values are their corresponding indices.
• We use slice() to create a copy of targetArray to avoid modifying the original.
• The sort function now directly compares the indices retrieved from indexMap.

3. The reduce and splice Technique: In-Place Sorting

This method modifies the target array directly, making it more memory-efficient for large datasets. * When to Use: When memory usage is a concern and you don’t need to preserve the original order of the target array. * How it Works:

   const sortingArray = ['c', 'a', 'b'];
   const targetArray = ['b', 'c', 'a'];

   const indexMap = sortingArray.reduce((acc, element, index) => {
     acc[element] = index;
     return acc;
   }, {});

   targetArray.sort((a, b) => indexMap[a] - indexMap[b]);

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

• We use reduce to create the indexMap object in a more concise way.
• The sort function directly modifies targetArray in place.

4. The Array.from and findIndex Combination: Readability and Flexibility

This approach prioritizes readability and leverages modern JavaScript features. * When to Use: When code clarity is important and you want a more expressive solution. * How it Works:

   const sortingArray = ['c', 'a', 'b'];
   const targetArray = ['b', 'c', 'a'];

   const sortedArray = Array.from(targetArray, element => ({
     element,
     index: sortingArray.findIndex(e => e === element)
   })).sort((a, b) => a.index - b.index)
   .map(item => item.element);

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

• Array.from creates a new array from targetArray, mapping each element to an object with its value and corresponding index found using findIndex.
• The rest of the process is similar to the first method.

5. The Lodash _.sortBy Utility: Leveraging Libraries

If you’re already using Lodash in your project, its _.sortBy function provides a concise and efficient solution. * When to Use: When you’re already using Lodash and want a quick and reliable solution. * How it Works:

   const _ = require('lodash');

   const sortingArray = ['c', 'a', 'b'];
   const targetArray = ['b', 'c', 'a'];

   const sortedArray = _.sortBy(targetArray, element => sortingArray.indexOf(element));

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

• _.sortBy takes an array and an iteratee function that returns the value used for sorting.

Remember, the best approach depends on your specific requirements. Experiment with these methods and choose the one that best suits your project’s needs.