jquery - addClass vs attr and creating an ID -

So what I am reading is that when an element is added without specifying a class already, Also use addClass ()

For example,

  .addClass ('myclass') using   
 The more efficient I can add anything to the addId ('Married') to add the ID selectors, I / I> 
  .attr ('class',' myclass ')   
 This is present or the most to add the ARR (ID) selector Good way  
 I think this ID is unique, the reason behind my question is that the addClass () is faster than attr ().  
 So my question is if there is a more efficient method to create an ID from atr ().   
 
      < /      may be more than the attribute  and 
 Change the function of so many jQuery  addClass ()  class attribute helps to add value. Similarly, the work  toggleclass ()  and 'removeClass () `help in manipulating them.  
 But the function  attr ()  will only manipulate the attribute and change it directly.  
 For example:  
  & lt; Div id = "person" & gt; No & lt; / Div & gt;   
 and the following jQuery statement  
  $ ("# div"). AddClass ("tall"); // This will create a class attribute and add a long $ ("# div"). AddClass ("fat"); // It will add fat to the existing class and make "tall fat" $ ("# div"). Adclass ("gray"); // same   
  .addClass ()  will just add the class name. If you only need one using the  attr ()  then you have to do  
  $ ("# div"). Attr ('class', 'tall'); $ ("# Div"). Ether ('square', 'tall fat'); $ ("# Div"). Ether ('class', 'tall fat brown');   
 Or, you can modify the attribute using  
  $ ("# div"). Attr ('class', function (i, className) {return classname + "brown";});   
 Where  id  has a value that needs to be modified or changed, so the function like  addId ()  must be done correctly ('Id', 'idvalue').