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closure in js

A closure gives you access to an outer function’s scope from an inner function
//example
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();
Comment

Closure ()

// Closures
// In JavaScript, closure is one of the widely discussed and important concepts.
// A closure is a function that has access to the variable from another function’s scope which is accomplished by creating a function inside a function. As defined on MDN:
// “Closures are functions that refer to independent (free) variables. In other words, the function defined in the closure ‘remembers’ the environment in which it was created.”
// In JavaScript, closures are created every time a function is created, at function creation time. Most JavaScript developers use closure consciously or unconsciously — but knowing closure provides better control over the code when using them.
// Example:

function Spellname(name) {
var greet = "Hi, " + name + "!";
var sName = function() {
var welc = greet + " Good Morning!";
console.log(greet);
};
return sName;
}
var Myname = SpellName("Nishi");
Myname();  // Hi, Nishi. Good Morning!

// In the above example, the function sName() is closure; it has its own local scope (with variable welc) and also has access to the outer function’s scope. After the execution of Spellname(), the scope will not be destroyed and the function sName() will still have access to it.

Comment

closure in javascript

-->closure in javascript
//closure is the combination of function and the lexical enviornment in
//which the function is defined.closure give you access to the functions
//and variables outside the function.
function outer(){
  const outerData ="outer";
  function inner(){
    const innerData="inner";
    console.log(`${outerData} and{innerData}`);
  }
  inner();
}
outer();
Comment

closures in javascript

// A closure is a function having access to the parent scope, 
// even after the parent function has popped.

function greeting() {
    let message = 'Hi';

    function sayHi() {
        console.log(message);
    }

    return sayHi;
}
let hi = greeting();
hi(); // still can access the message variable
Comment

javascript closure

function makeAdder(x) {
  return function(y) {
    return x + y;
  };
}

var add5 = makeAdder(5);
var add10 = makeAdder(10);

console.log(add5(2));  // 7
console.log(add10(2)); // 12
Comment

how javascript closures work?

function foo() {
  const secret = Math.trunc(Math.random() * 100)
  return function inner() {
    console.log(`The secret number is ${secret}.`)
  }
}
const f = foo() // `secret` is not directly accessible from outside `foo`
f() // The only way to retrieve `secret`, is to invoke `f`
 Run code snippet
Comment

closure in javascript

function makeFunc() {
  var name = 'Mozilla';
  function displayName() {
    alert(name);
  }
  return displayName;
}

var myFunc = makeFunc();
myFunc();
Comment

javascript closure

function makeAdder(x) {
  return function(y) {
    return x + y;
  };
}

var add5 = makeAdder(5);
var add10 = makeAdder(10);

console.log(add5(2));  // 7
console.log(add10(2)); // 12

//my words: what this code do is basically a nested function that will return
//its inner function (un-activated). So var add5 in line 7 activated the outer
//function with 5 as parameter which makes add5 is now the nameless function at
//line 2 that will return 5 + y;

//MDN words:
//add5 and add10 are both closures. They share the same function body
//definition, but store different lexical environments. In add5's lexical
//environment, x is 5, while in the lexical environment for add10, x is 10.
Comment

js closure examples

function outer() {
  var counter = 0; // Backpack or Closure
  function incrementCounter() {
    return counter++;
  }
  return incrementCounter;
}

const count = outer();
count(); // 0
count(); // 1
count(); // 2
Comment

what is closure in javascript

function OuterFunction() {

    var outerVariable = 100;

    function InnerFunction() {
        alert(outerVariable);
    }

    return InnerFunction;
}
var innerFunc = OuterFunction();
Comment

JavaScript - Closures

function makeAdder(x) {
  return function(y) {
    return x + y;
  };
}

var add5 = makeAdder(5);
var add10 = makeAdder(10);

console.log(add5(2));  // 7
console.log(add10(2)); // 12

//=====
//add5 and add10 are both closures. 
//They share the same function body definition, but store different lexical environments. 
//In add5's lexical environment, x is 5, while in the lexical environment for add10, x is 10.
Comment

js closure

// 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
Comment

Closure Example


	 function Counter() {
    var counter = 0;
alert("XXXXX");
function increaseCounter()
{
return counter +=1;
} 

return increaseCounter;
}

/***/
const counter = new Counter();
console.log(counter());
console.log(counter());


/*note that alert("XXXX") only executes once*/
/*think of counter() = new Counter() declaration as storing the value of ONE Counter function execution and 
the remaining times you use counter(), you reexecute only the returned function*/
/*use counter() instead of Counter() if you want alert("XXXX") to execute only once AND for you to be able to return an actual value otherwise you only console.log a function and alert executes multiple times*/
Comment

closure in javascript

var counter = (function() {
  var privateCounter = 0;
  function changeBy(val) {
    privateCounter += val;
  }
  return {
    increment: function() {
      changeBy(1);
    },
    decrement: function() {
      changeBy(-1);
    },
    value: function() {
      return privateCounter;
    }
  };
})();

console.log(counter.value()); // logs 0
counter.increment();
counter.increment();
console.log(counter.value()); // logs 2
counter.decrement();
console.log(counter.value()); // logs 1
Comment

what is a closure in javascript

// A Closure gives you access to an outer function's scope from an inner function.
// Example
function myNameIs(name) {
  return function(){
  	console.log('Hi my name is ' + name);
  }
}

let maxine = myNameIs('Maxine');
let amber = myNameIs('Amber');

maxine();
amber();
Comment

javascript closure

function numberGenerator() {
  // Local “free” variable that ends up within the closure
  var num = 1;
  function checkNumber() { 
    console.log(num);
  }
  num++;
  return checkNumber;
}

var number = numberGenerator();
number(); // 2
Comment

How do JavaScript closures work?

/*
A lexical environment is part of every execution context (stack frame) and is a map between identifiers (i.e. local variable names) and values.

Every function in JavaScript maintains a reference to its outer lexical environment. This reference is used to configure the execution context created when a function is invoked. 
This reference enables code inside the function to "see" variables declared outside the function, regardless of when and where the function is called.

If a function was called by a function, which in turn was called by another function, then a chain of references to outer lexical environments is created.
This chain is called the scope chain.

In the following code, inner forms a closure with the lexical environment of the execution context created when foo is invoked, closing over variable secret:
*/
function foo() {
  const secret = Math.trunc(Math.random() * 100)
  return function inner() {
    console.log(`The secret number is ${secret}.`)
  }
}
const f = foo() // `secret` is not directly accessible from outside `foo`
f() // The only way to retrieve `secret`, is to invoke `f`
 Run code snippet
Comment

Javascript Closure

function makeFunc() {
  var name = 'Mozilla';
  function displayName() {
    alert(name);
  }
  return displayName;
}

var myFunc = makeFunc();
myFunc();
Comment

closure in javascript

//Closures
Closures means a function bind together with its lexical environment
                           	OR
You can say a function along with its lexical scope bundle together forms
a closure
                            OR
In other words, a closure gives you access to an outer function's
scope from an inner function.
//Example
function x(){
  var a = 7;
  function y(){    //function y bind with its lexical enviroment
    console.log(a); 
  }
  a = 100;
  return y;
}
var z = x();
console.log(z) //Output is 100 
Comment

JavaScript Closures

// javascript closure example

// outer function
function greet() {
    // variable defined outside the inner function
    let name = 'John';
    // inner function
    function displayName() {

        // accessing name variable
        return 'Hi' + ' ' + name;
      
    }
    return displayName;
}

const g1 = greet();
console.log(g1); // returns the function definition
console.log(g1()); // returns the value
Comment

closure in javascript

// Explanation of closure
/* 1 */        function foo()
/* 2 */         {
/* 3 */             var b = 1;
/* 4 */             function inner(){
/* 5 */                 return b;
/* 6 */             }
/* 7 */             return inner;
/* 8 */         }
/* 9 */         var get_func_inner = foo();        
 
/* 10 */         console.log(get_func_inner());
/* 11 */         console.log(get_func_inner());
/* 12 */         console.log(get_func_inner());
Comment

Closures in javascript

let counter = (function() {
    let i = 0; // private property

    return {   // public methods
        get: function() {
            alert(i);
        },
        set: function(value) {
            i = value;
        },
        increment: function() {
            alert(++i);
        }
    };
})(); // module

counter.get();      // shows 0
counter.set(6);
counter.increment(); // shows 7
counter.increment(); // shows 8
Comment

A closure Function

var returns_a_func = function () {
  var word = 'I can see inside '     function sentence(){    var word2 = 'I can also see outside. '     console.log(word + 'and ' + word2)   }   return sentence;
}var finalSentence = returns_a_func()finalSentence()
Comment

what is closure in javascript

document.getElementById('size-12').onclick = size12;
document.getElementById('size-14').onclick = size14;
document.getElementById('size-16').onclick = size16;
Comment

what is a closure in javascript

//Closures are the inner functions that are embedded in parent function
function getName(){
    // print name function is the closure since it is child function of getName
     function printName(){
         return 'Kevin'
     }
     // return our function definition
     return printName;
}

const checkNames = getName();
console.log(checkNames());
Comment

function - How do JavaScript closures work?

function createObject() {
  let x = 42;
  return {
    log() { console.log(x) },
    increment() { x++ },
    update(value) { x = value }
  }
}

const o = createObject()
o.increment()
o.log() // 43
o.update(5)
o.log() // 5
const p = createObject()
p.log() // 42
Comment

js closure

function aFunc(x){
  return () => console.log( x++ )
}
Comment

closure in javascript

A closure is a function bundeled together with its lexical scope
Comment

What is Closures in JavaScript

/*A closure is the combination of a function bundled together (enclosed) with references
to its surrounding state (the lexical environment). In other words, a closure gives you 
access to an outer function’s scope from an inner function. In JavaScript, closures are 
created every time a function is created, at function creation time.*/

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();
Comment

closure example

const add = (function () {
  let counter = 0;
  return function () {counter += 1; return counter}
})();

add();
add();
add();

// the counter is now 3
Comment

JavaScript Closures

function myFunction() {
  let a = 4;
  return a * a;
}
Comment

A closure Function

Cannot GET /about-us.html
Comment

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