arrayunshift

Arrayunshift is a JavaScript array method that adds one or more elements to the beginning of an array. It modifies the original array and returns the new length of the array.

The syntax for arrayunshift is array.unshift(element1, element2, ..., elementN). The elements can be of any data type.

For example, if you have an array `myArray = [2, 3, 4]` and you call `myArray.unshift(1)`, the array will become `[1, 2, 3, 4]`. If you call `myArray.unshift(-1, 0)`, the array will become `[-1, 0, 1, 2, 3, 4]`. The method also returns the new length of the array. In the first example, it would return 4, and in the second, it would return 6.

Arrayunshift is often contrasted with arraypush, which adds elements to the end of an array. Unlike some other array manipulation methods that might create a new array, arrayunshift directly alters the array it is called upon. This in-place modification can be efficient for certain operations but requires awareness that the original array is changed.

The performance of arrayunshift can vary depending on the JavaScript engine and the number of elements being added. Adding many elements or operating on very large arrays might have performance implications due to the need to re-index all existing elements.