JavaScript Interview Questions Advanced and Broad Topic

    // JavaScript Interview Questions Advanced and Broad Topic
    // Closures
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures
    // https://jsfiddle.net/xAFs9/3/
    // lexical scoping
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures#practical_closures 
    // jciq;01
    // https://30secondsofinterviews.org/
    
    
    function init() {
      var name = 'Mozilla'; // name is a local variable created by init
      function displayName() { // displayName() is the inner function, a closure
        alert(name); // use variable declared in the parent function
      }
      displayName();
    }
    init();
    
    
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures#practical_closures
    
    // global scope
    var e = 10;
    function sum(a){
      return function(b){
        return function(c){
          // outer functions scope
          return function(d){
            // local scope
            return a + b + c + d + e;
          }
        }
      }
    }
    
    console.log(sum(1)(2)(3)(4)); // log 20
    
    // You can also write without anonymous functions:
    
    // global scope
    var e = 10;
    function sum(a){
      return function sum2(b){
        return function sum3(c){
          // outer functions scope
          return function sum4(d){
            // local scope
            return a + b + c + d + e;
          }
        }
      }
    }
    
    var sum2 = sum(1);
    var sum3 = sum2(2);
    var sum4 = sum3(3);
    var result = sum4(4);
    console.log(result) //log 20
    
    // In the example above, there's a series of nested functions, all of which have access to the outer functions' 
    // scope. In this context, we can say that closures have access to all outer function scopes.