[AndrewGSW]

We could use it to create list and dictionary comprehensions . Or our own slice() method:

function listSlice(element, index, array) {
    if (!this[2]) this[2] = array.length - 1;
    if (index >= this[1] && index <= this[2]) {
        this[0].push(element);
    }
}
var a = [ 2, 5, 9, 8, 6 ], b = [];
a.forEach(listSlice, [b, 2]);


console.log(a); // [ 2, 5, 9, 8, 6 ]
console.log(b); // [ 9, 8, 6 ]