A closure adalah fungsi sing diikat bareng karo referensi marang variabel saka lingkungan leksial (scope) ing saubengé. Merga closure, fungsi inner tetep bisa ngakses variabel fungsi outer sanajan fungsi outer wis bali.
() {
count = ;
{
: ++count,
: count,
};
}
a = ();
b = ();
a.(); a.();
b.();
count ora bisa diakses saka luar — mung inc/get sing bisa neoni. Iku data privacy sing dibangun saka closure. Lan saben panggilan makeCounter() nggawe scope anyar sing terpisah.
for (var i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 0); // prints 3, 3, 3 — all share one `i`
}
for (let i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 0); // prints 0, 1, 2 — `let` is per-iteration
}
Karo var, saben callback nutup luwih i sing padha (sing dadi 3 nalika bakal dilakokke). let nggawe binding anyar saben iterasi.
Closures nduweni kakuwatan module privacy, memoization, currying, event handlers/callbacks sing ngengo-ingat state, lan persis carane React hooks (useState) tetepake nilai antarane renders.
Pustaka pitakon wawancara IT kanthi jawaban rinci — saka Junior nganti Senior.
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