callback.js

exports.checkingUser = function (req,res,callback)
{
    ....
    ....
    self = this;
    this.getAllUser(database,function(err,docs)
    {
       if(err)
	{
		return callback(err);
	}
	
	self.checkingPhoneSystem (datbase, docs, function(err,docs)
	{
	       if(err)
		{
			return callback(err);
		}
		callback(null,docs);
	});
    }
}

exports.checkingPhoneSystem(database,docs,callback)
{
	for(var k=0 ; k < docs.length ; k++)
	{
		var person = docs[k];
		
		for(var k=0 ; k < person.phoneNumbers.length ; k++)
		{
			.....
			.....
			callback(true);
		}
	}
}

callbackerror.js

var person = docs[k];

for(var k=0 ; k < person.phoneNumbers.length ; k++)
  	{
			.....
			.....
			callback(true);
		}

fixcallback.js

var person = docs[k];
 
if(person.phoneNumber.length == 0)
{
	callback(false);
}
for(var k=0 ; k < person.phoneNumbers.length ; k++)
    {
			.....
			.....
			callback(true);
		}