toComplexArray(input, storage) {
        const res = storage || this.createComplexArray();
        for (let i = 0; i < res.length; i += 2) {
            res[i] = input[i >>> 1];
            res[i + 1] = 0;
        }
        return res;
    }
Convert a real-valued input array to a complex-valued output array.
@param {Float64Array} input The real-valued input array.
@param {Float64Array} [storage] Optional buffer to store the output array.
@returns {Float64Array} The complex-valued output array.