Nodejs appears double callback! Prompt

  node.js, question
function get_content(url, callBack){
 var obj = {};
 obj.url = url;
 obj.cookie = pickInfo.cookie;
 get(obj, callBack);
 bracket
function get(obj, callBack){
 
 charset(superagent).get(obj.url).charset().end(function(err,res) {
 var status = res.status;
 if(status == 200){
 callBack(res);
 }else{
 Log ("failed" plus err);
 bracket
 
 });
 
 
 bracket

Then I call get_content and this appears. According to the tip, it should be double tone or something, is there a problem with this writing? How should it be improved?

What you don’t understand inside hinders analysis, such as:charsetWhat is it? Why call twice?