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JavaScriptで秒を数えるいくつかの方法

Last updated at 2018-11-07Posted at 2018-10-11

####普通の書き方

let i = 0;
const update = () => {
  console.log(i);
  i++;
}
setInterval(update, 1000);

####再帰関数

const update = (i = 0) => {
  console.log(i);
  return setTimeout(() => update(i + 1), 1000);
};
update();

####クロージャー

const update = () => {
  let i = 0;
  return () => console.log(i++);
};
setInterval(update(), 1000);

短く書くと

const update = (i = 0) => () => console.log(i++);
setInterval(update(), 1000);

####Promise

(async() => {
  for (let i = 0; true; i++) {
    await new Promise(res => setTimeout(res, 1000));
    console.log(i);
  }
})();