Compute any-Base Exponential

console.log(Math.pow(7, 3));
// expected output: 343

console.log(Math.pow(4, 0.5));
// expected output: 2

console.log(Math.pow(7, -2));
// expected output: 0.02040816326530612
//                  (1/49)

console.log(Math.pow(-7, 0.5));
// expected output: NaN

// simple
Math.pow(7, 2);    // 49
Math.pow(7, 3);    // 343
Math.pow(2, 10);   // 1024
// fractional exponents
Math.pow(4, 0.5);  // 2 (square root of 4)
Math.pow(8, 1/3);  // 2 (cube root of 8)
Math.pow(2, 0.5);  // 1.4142135623730951 (square root of 2)
Math.pow(2, 1/3);  // 1.2599210498948732 (cube root of 2)
// signed exponents
Math.pow(7, -2);   // 0.02040816326530612 (1/49)
Math.pow(8, -1/3); // 0.5
// signed bases
Math.pow(-7, 2);   // 49 (squares are positive)
Math.pow(-7, 3);   // -343 (cubes can be negative)
Math.pow(-7, 0.5); // NaN (negative numbers don't have a real square root)
// due to "even" and "odd" roots laying close to each other, 
// and limits in the floating number precision, 
// negative bases with fractional exponents always return NaN
Math.pow(-7, 1/3); // NaN