Javascript DOM "radio checked"

I used the radio check to change the image.

Here is my html file.

The is the webpage has a boy image. I want to change the image of eye, mouth and nose.

 

As we can see, the image should be changed when I check another radio. I put the "onclick=" to call the javascript function.

 

Each function has two var. "var ~Radio" is for array to get Node from html file. "var ~Image" includes the node from <img> in html. 

First radio option will be located in the first variable in array. if((var).checked) figures out which radio we check on the html file. Following that, I change the source of <img>.