“O que são fechamentos” Respostas de código

Fecho ()

// 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.

Meandering Meerkat

JavaScript - Fechamentos

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.
The Arborist

Fechamento em 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
Gentle Grouse

O que são fechamentos

Closures are related and often confused with lambda functions.
The 2 concepts are wonderfully explained and distinguished 
in this StackOverflow answer :
https://stackoverflow.com/a/36878651/13574304
Lively Lion

Como funcionam os fechamentos de JavaScript?

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
Himanshu Jangid

O que é o fechamento em JavaScript

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

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