Find exponent of imaginary number in JavaScript

imaginaryExponent.js

function imaginaryExponent(exponent) {
    switch(exponent % 4) {
        case 1:
            return 'i';
            break;
        case 2:
            return -1;
            break;
        case 3:
            return '-i';
            break;
        case 4:
            return 1;
            break;
    }
}