Hello,

Traditional javaScript function has the Method, Non-methods and constructor and have their own this keyword, so it causes the this binding.  To overcome this problem coffeeScript provides an Arrow function, Called "javaScript arrow" Function or " fat Arrow " function. It is an anonymous function and can not be used as constructor. Its behaviours is different  as compare to the traditional javaScript behavior in the following manner:-

• Lexical this binding.
• Not newable.
• Can not change this.

It has the following characteristic of the arrow function:-

• JavaScript arrow function are anonymous function.
• Arrow function can not be used as a constructor function.
• Lexical binding of this inside arrow function that means this keyword always point out the same function throughout the arrow function.

 The Syntax:- Here is some example of the syntax of the arrow function.

• No Parameter:-                                                                                                                       

  /no params, empty body
  () => {};
  
  //equivalent to
  function(){}

   

• With single Parameter:-                                                                                                          

  //single param, single statement
  x => x;
  
  //traditional function with single parameter
  
  function(x){
      return x;
  }

   

• With multiple params:- 

  //multiple params
  (x, y) => x * y;
  
  
  //traditional function with multiple params
  
  
  function(x, y){
      return x * y;
  }

   

• Multiple params and statements:-

  (x, y) => {
      var z = 5;
      return (x * y) + z;
  }

• Wrap function BODY in parenthesis:-

  x => ({id: x, height: 270});

   

The javascript arrow function can be remember by following rules:-

• We can omit the () for the single parameter arrow function.
• We can wrap the parameters in the () for the multiple parameters or no parameters arrow function. 

The lexical this  binding can solve the many problem as compare to the traditional javascript function for the developer. It improves the javascript engine optimization as compare to the traditional javascript function. It concise the syntax also.