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sashee/index.html

Last active January 9, 2020 10:39
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index.html
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js" integrity="sha256-G7A4JrJjJlFqP0yamznwPjAApIKPkadeHfyIwiaa9e0=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/bluebird/3.7.2/bluebird.min.js" integrity="sha256-vV2kNkyUsRqeVvDQOIQ5CC7207KcFSVawXutQKvgwkg=" crossorigin="anonymous"></script>
</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("sync map");
const arr = [1, 2, 3];
const syncRes = arr.map((i) => {
return i + 1;
});
console.log(syncRes);
// 2,3,4
}
{
console.log("\nasync map")
const arr = [1, 2, 3];
const asyncRes = await Promise.all(arr.map(async (i) => {
await sleep(10);
return i + 1;
}));
console.log(asyncRes);
// 2,3,4
}
{
console.log("\nmap in groups");
const arr = [30, 10, 20, 20, 15, 20, 10];
const mapInGroups = (arr, iteratee, groupSize) => {
const groups = _.groupBy(arr, (_v, i) => Math.floor(i / groupSize));
return Object.values(groups)
.reduce(async (memo, group) => [
...(await memo),
...(await Promise.all(group.map(iteratee)))
], []);
};
const res = await mapInGroups(arr, async (v) => {
console.log(`S ${v}`);
await sleep(v);
console.log(`F ${v}`);
return v + 1;
}, 3);
// -- first batch --
// S 30
// S 10
// S 20
// F 10
// F 20
// F 30
// -- second batch --
// S 20
// S 15
// S 20
// F 15
// F 20
// F 20
// -- third batch --
// S 10
// F 10
console.log(res);
// 31,11,21,21,16,21,11
}
{
console.log("\nparallel map");
const arr = [30, 11, 22, 23, 14, 25, 16];
// Bluebird promise
const res = await Promise.map(arr, async (v) => {
console.log(`S ${v}`)
await sleep(v);
console.log(`F ${v}`);
return v + 1;
}, {concurrency: 2});
// S 30
// S 11
// F 11
// S 16
// F 30
// S 25
// F 16
// S 14
// F 14
// S 23
// F 25
// S 22
// F 23
// F 22
console.log(res);
// 31,12,23,24,15,26,17
}
{
console.log("\nserial map");
const arr = [1, 2, 3];
const res = await arr.reduce(async (memo, v) => {
const results = await memo;
console.log(`S ${v}`)
await sleep(10);
console.log(`F ${v}`);
return [...await results, v + 1];
}, []);
// S 1
// F 1
// S 2
// F 2
// S 3
// F 3
console.log(res);
// 2,3,4
}
{
console.log("\nsync reduce");
const arr = [1, 2, 3];
const syncRes = arr.reduce((memo, e) => {
return memo + e;
}, 0);
console.log(syncRes);
// 6
}
{
console.log("\nasync reduce");
const arr = [1, 2, 3];
const startTime = new Date().getTime();
const asyncRes = await arr.reduce(async (memo, e) => {
await sleep(10);
return (await memo) + e;
}, 0);
console.log(asyncRes);
// 6
console.log(`Took ${new Date().getTime() - startTime} ms`);
// Took 11-13 ms
}
{
console.log("\nsync filter");
const arr = [1, 2, 3, 4, 5];
const syncRes = arr.filter((i) => {
return i % 2 === 0;
});
console.log(syncRes);
// 2,4
}
{
console.log("\nasync filter");
const arr = [1, 2, 3, 4, 5];
const asyncFilter = async (arr, predicate) => {
const results = await Promise.all(arr.map(predicate));
return arr.filter((_v, index) => results[index]);
}
const asyncRes = await asyncFilter(arr, async (i) => {
await sleep(10);
return i % 2 === 0;
});
console.log(asyncRes);
// 2,4
}
{
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
}
{
console.log("\nsync some");
const arr = [1, 2, 3];
const res = arr.some((i) => {
console.log(`Checking ${i}`);
return i % 2 === 0;
});
// Checking 1
// Checking 2
console.log(res);
// true
}
{
console.log("\nasync some");
const arr = [1, 2, 3];
const asyncSome = async (arr, predicate) => {
for (let e of arr) {
if (await predicate(e)) return true;
}
return false;
};
const res = await asyncSome(arr, async (i) => {
console.log(`Checking ${i}`);
await sleep(10);
return i % 2 === 0;
});
// Checking 1
// Checking 2
console.log(res);
// true
}
{
console.log("\nsync every");
const arr = [1, 2, 3];
const res = arr.every((i) => {
console.log(`Checking ${i}`);
return i < 2;
});
// Checking 1
// Checking 2
console.log(res);
// false
}
{
console.log("\nasync every");
const arr = [1, 2, 3];
const asyncEvery = async (arr, predicate) => {
for (let e of arr) {
if (!await predicate(e)) return false;
}
return true;
};
const res = await asyncEvery(arr, async (i) => {
console.log(`Checking ${i}`);
await sleep(10);
return i < 2;
});
// Checking 1
// Checking 2
console.log(res);
// false
}
})();
</script>
</body>
</html>
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