I wish to merge one array into an existing array in-place without copying large arrays. For example:
let alpha = [1, 2];
let beta = [3, 4, 5];
combineInPlace(alpha, beta);
// alpha is now [1, 2, 3, 4, 5]
What method should I use?
you can simply loop thru beta and push each element into alpha. for example, use a for loop to accomplish it in place. works fine in all js engines and keeps your memory usage low if spread isnt ideal.
Based on my experience, using in-place array modification is simplest with the built-in push method together with the spread operator. This approach allows you to effectively append elements from one array into another like this: alpha.push(…beta). This method directly mutates alpha without creating a new array, which is ideal when working with large datasets. It’s a concise solution and works well in most modern environments. However, if compatibility with older browsers is required, a simple iterative approach may be necessary instead.
Based on my experience managing large datasets in JavaScript, I recommend using the built-in push method in combination with Function.prototype.apply if browser support for spread operator is an issue. This technique, which uses Array.prototype.push.apply(alpha, beta), efficiently merges another array into your original array without creating a separate copy and offers robust performance even with a considerable number of elements. In my projects, I encountered scenarios where this in-place merging was necessary to maintain memory efficiency and operational simplicity.
In one of my projects, I discovered that iterating over the indices and directly assigning them to the target array can be surprisingly effective. Instead of using push or apply, I simply determine the current length of the destination array and then assign each element of the source one by one at the appropriate index. This technique reduces function call overhead and works efficiently with large arrays, as it leverages simple arithmetic with the index. I found it to be particularly beneficial in performance-critical sections when memory usage and processing speed were equally important.
Another viable approach is to empty the source array while appending its elements directly into the destination array. This method is best suited when the source array is no longer needed afterwards. For instance, using a while loop: while(beta.length) { alpha.push(beta.shift()); } effectively transfers elements from beta to alpha in place. With this approach, no additional array is created. I applied this method in several scenarios where memory constraints were critical and found it quite effective, especially when working with mutable data sets.