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sashee/index.html

Created January 10, 2020 08:43
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index.html
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
</head>
<body>
<script>
console.log = (msg) => document.body.innerText += `${msg}\n`;
// utility function for sleeping
const sleep = (n) => new Promise((res) => setTimeout(res, n));
(async () => {
{
console.log("\nsync forEach");
const arr = [1, 2, 3];
arr.forEach((i) => {
console.log(i);
});
// 1
// 2
// 3
console.log("Finished sync");
// Finished sync
}
{
console.log("\nasync forEach");
const arr = [1, 2, 3];
arr.forEach(async (i) => {
await sleep(10 - i);
console.log(i);
});
console.log("Finished async");
// Finished async
// 3
// 2
// 1
}
await sleep(20);
{
console.log("\ncontrolled forEach");
const arr = [1, 2, 3];
await Promise.all(arr.map(async (i) => {
await sleep(10 - i);
console.log(i);
}));
// 3
// 2
// 1
console.log("Finished async");
// Finished async
}
{
console.log("\nserialized forEach");
const arr = [1, 2, 3];
await arr.reduce(async (memo, i) => {
await memo;
await sleep(10 - i);
console.log(i);
}, undefined);
// 1
// 2
// 3
console.log("Finished async");
// Finished async
}
})();
</script>
</body>
</html>
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