/* See question for more context on this code: - https://www.sololearn.com/Discuss/669904/please-illustrate-javascript-closure-with-example */ //Global scope var max_attempts_allowed = 5; //Global Scope: Parent function with a nested function closure. var do_something = (function(){ //Private Scope: attempts is like a private variable. var attempts = 0; //Number of times something is done. //Private Scope function available only to the closure. var action_allowed = function(){ log("

Attempts: " + attempts + "

", false); } //Another private Scope function available only to the closure. var action_restricted = function(){ log("

Max Attempts Exceeded (based on private variable: attempts value)

", false); } //This closure has access to the private scope of the do_something() function. return function (){ //Comparing the private scope variable against the global scope variable. if(attempts < max_attempts_allowed){ attempts += 1; //Increments the variable that is in the parent function scope. action_allowed(); } else { action_restricted(); } } })(); //Global scope var check_scope = function(name, type){ var is_inscope = type != "undefined"; var font_color = is_inscope ? "green" : "red"; log( "

" + name + " is " + type + "

", false ); } //Global scope var log = function(message="", add_line_break = true){ document.write(message + (add_line_break ? "
" : "")); } log("

Test calling a function with a closure:

", false); log("

", false); //This loop will end up exceeding the max_attempts_allowed for calling do_something() for(let i = 0; i <= max_attempts_allowed+4; i++) { do_something(); } log("", false); log("

Test to show global scope variables are accessible (as expected):

", false); log("

", false); check_scope("global scope: var max_attempts_allowed", typeof max_attempts_allowed); check_scope("global scope: function do_something()", typeof do_something); check_scope("global scope: function check_scope()", typeof check_scope); check_scope("global scope: function log()", typeof log); log("", false); log("

Test to show private scope is NOT accessible outside of the closure:

", false); log("

", false); check_scope("private scope: var attempts", typeof attempts); check_scope("private scope: function action_allowed()", typeof action_allowed); check_scope("private scope: function action_restricted()", typeof action_restricted); log("", false);

Closure Demo