coding style - Providing a default string parameter in JavaScript -

I have always used the following syntax to ensure that the input variable is not null

  function F (input) {if (input === blank) input = ""; ...}   
 Recently, I have seen that it is low to express it as follows.  
  function f (input) {input = input? Input: ""; ...}   
 But also I have seen this syntax.  
  function f (input) {input = input || ""; ...}   
 
 Is not those equivalent ( what  is in but  how  they do)?  
 Most recommended (readability etc)?   
 Note that I will strictly work with the input of the wires as if it is either valid or empty). If I want to expand security to include other types, then should I consider additional issues?   "post-text" itemprop = "text"> 
 First of all, note that they are not all the same. # 2 and # 3 have exactly the same result: Unless the  input  is true, set it to empty string # 1 means "until  input  Is  null , set it to an empty string, so if  false  was provided,  false  false , But # 2 and # 3 will have  '' .  
 If nothing is not provided # 1, Code> F () ,  Input  will be  undefined , because it is the value Which passes when passed,  not null  
  if (input === undefined) if (input == zero)  
  input = input. ""   
 This is my favorite style. It can be yours, it can not happen. But, at the top,   be consistent  .  < / Div>