A real wok is made from high carbon steel .. it gets very hot very quickly - but it has temperature differances over it's surface - the higher up the sides the lower the temp. You can pull food up on the sides and throw something else into the bottom and heat it quickly and at a hotter temp while the food on the sides of the pan continue to cook at a lower temp.
Cast iron does not work that way - the heat is too even and it is very slow to come up to temp. And, from the testing that Cook's Illustrated/America's Test Kitchen did - an electric wok is better used as a deep fryer than for stir-frying.
There are some steel woks with flat bottoms that you can use on a glass top stove ... and there are some made from anodized aluminum. I would stay away from anything called a wok that is cast iron, coated with a nonstick surface, or stainless steel.
According to Joy of Cooking - Asian war brides (WWII and Korea) found a big flat skillet (aka a saute pan or chicken fryer pan) worked just as well.