Concatenating prefix of one array with the reversed suffix of another array
The only note I can make is that in func1 and func2 you have an "API bug": the indices are "included" in the array. Consider this example:

[1, 2, 3, 4].slice(1, 3)


will produce [2, 3], so the point is that 3 in slice(1, 3) is not included. This does not happen only in Javascript, but also in other languages as well (I know Java does it that way). So the only advice would be to write your functions as

function func1(arr1,arr2,ind1,ind2)
{
    let arr = [];
    for (let n = 0; n &lt; ind1; n++)
        arr.push(arr1[n]);
    for (let n = ind2 - 1; n &gt;= 0; n--)
        arr.push(arr2[n]);
    return arr;
}

function func2(arr1,arr2,ind1,ind2)
{
    return arr1.slice(0, ind1).concat(arr2.slice(0, ind2).reverse());
}


Also, it is good to have a single space after each comma , in the function parameter list.