Expert Developer JavaScript Interview Question:

Explain JavaScript closures by example?

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► The closure is a local variable of a function which remains alive after the function has returned.
► Closure combines a function with a local variable available at the time of creating closure.
► For example :
function wish(msg)
{
console.log(msg);
}
function greeting(name, occasion)
{
return name + ", Happy " + occasion;
}
var message = greeting ("Arpit", "Birthday");
// Pass it explicitly to wish
wish(message);
► By using closure we can simplify above code.
function greeting (name, occasion)
{
var msg = name + ", Happy " + occasion;
return function wish()
{
console.log(msg);
};
}
// create the closure
var wisharpit = greeting ("Arpit", "Birthday");

// use the closure
wisharpit ();
► Here wish function is nested within the greeting, so closure can access the local variable of greeting which are name, occasion and msg.
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