var base64_from_endpoint = 'data:image/png;base64,AAAFBfj42Pj4';
var image_data = base64_from_endpoint.replace(/^data:image\/png;base64,/, "");
var save_path='/tmp/';

require("fs").writeFile(save_path+'image.png', image_data, 'base64', function(result) {
    console.log(result);
});