files/functions.html

<!DOCTYPE html>
<html>
  <head>
    <title>Types of functions in JavaScript</title>
  </head>
  <script>
    // ----------------------
    // Hoisting functions()
    // ----------------------

    var expression = function(name) {
      console.log('Hi ' + name);
    };
    expression('Pradeep');

    /* * 
     *  Curray function
     *
     *  Currying is a process in functional programming in which we can transform a function with multiple arguments 
     *  into a sequence of nesting functions. It returns a new function that expects the next argument inline.
     * 
     * */
    function multiply(a) {
      return function(b) {
        return function(c) {
          return a * b * c;
        };
      };
    }
    console.log('Curray function: ' + multiply(1)(2)(3)); // 6

    /**
     *  Arrow Function()
     * 
     *  An arrow function expression is a syntactically compact alternative to a regular function expression, 
     *  although without its own bindings to the this, arguments, super, or new.target keywords. Arrow function 
     *  expressions are ill suited as methods, and they cannot be used as constructors.
     * 
     * **/
     
     var materials = [
        'Hydrogen',
        'Helium',
        'Lithium',
        'Beryllium'
    ];
    console.log('Arrow Function: ' + materials.map(material => material.length));

    const addition = (x, y) => { return x + y };
    console.log('addition: ' + addition(10, 20));

    /**
     *   Constructor Function()
     * 
     *   The Function constructor creates a new Function object. Calling the constructor directly can 
     *   create functions dynamically, but suffers from security and performance issues to eval. 
     *   However, unlike eval, the Function constructor creates functions which 
     *   execute in the global scope only.
     *  
     * **/

     var sum = new Function('a', 'b', 'return a + b');
     console.log('sum: ' + sum(10, 20)); // 30

     /**
      *   unescape() Function
      *   
      *   Note:- The unescape() function was deprecated in JavaScript version 1.5. Use decodeURI() or decodeURIComponent() instead.
      * 
      * **/

        var url = "https://www.google.co.in/?gfe_rd=cr&ei=VmKuWJ_EAcqBoAOrwZ2YDg";
        var url_esc = escape(url);
        var url_unesc = unescape(url);

        console.log('escape URL: ' + escape(url));    
        console.log('unescape URL: ' + unescape(url));  

    /***
     *  Callback function()
     * 
     *  A callback is a function that is to be executed after another function has finished executing.
     * 
     *  A callback function is a function passed into another function as an argument, which is then 
     *  invoked inside the outer function to complete some kind of routine or action.
     *  
     ***/
        
        function greeting(name) {
            alert('Hello ' + name);
        }
        function processUserInput(callback) {
            var name = prompt('Please enter your name: ');
            callback(name);
        }
        processUserInput(greeting);

  </script>
  <body>
    <h1>Types of functions in JavaScript</h1>
  </body>
</html>