How Can I Extend JavaScript Arrays Without Creating a New Array?

Extending Arrays in JavaScript without Creation

In JavaScript, it is common to encounter scenarios where we need to append the contents of one array to another without creating a new array. Unlike Python's extend method, JavaScript does not provide a built-in solution for this task.

To achieve this, we can utilize the .push method, which can take multiple arguments. By spreading the elements of the second array into the .push method using the ... operator, we can effectively add them to the first array:

a.push(...b);

If your browser doesn't support ECMAScript 6, you can use the .apply method as an alternative:

a.push.apply(a, b);

This approach is efficient for small arrays (b). However, if b is too large, it can lead to a stack overflow error. In such cases, using a standard loop-based technique is more suitable:

for (let i = 0; i < b.length; i++) {
  a.push(b[i]);
}

Remember that all of these solutions fail beyond a certain array size (approx. 100,000 elements) due to potential stack overflow errors. To handle larger arrays, implementing a custom extend method that does not create a new array is necessary.

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