The ECMAScript specification for Math.pow has the following peculiar rule:
Math.pow
If x < 0 and x is finite and y is finite and y is n
You can use a helper function.
In swift I faced a similar situation. Here is a proposed solution for you:
function checkSquareRoot(x, y) { if (x > 0) { return Math.pow(x, y) } return -1 * Math.pow(-x, y) }