Learning JavaScript Data Structures and Algorithms - Third Edition

Using the copyWithin method

The copyWithin method copies a sequence of values of the array into the position of a start index. For example, let's consider the following array:

let copyArray = [1, 2, 3, 4, 5, 6]; 

Now, let's say we want to copy the values 4, 5, and 6 to the first three positions of the array, resulting in the [4,5,6,4,5,6] array. We can use the following code to achieve this result:

copyArray.copyWithin(0, 3); 

Now, consider that we want to copy the values 4 and 5 (the positions 3 and 4) to the positions 1 and 2. We can use the following code to do this:

copyArray = [1, 2, 3, 4, 5, 6]; 
copyArray.copyWithin(1, 3, 5); 

In this case, we will copy the elements starting in position 3 and ending in position 5 (not inclusive) to ...