0.1.10 • Published 3 years ago
aih v0.1.10
Async iterable helpers aka aih
Since node 10, stream (fs, mongo cursor, http get, ect) are considered as async iterable. So I have decided to create some helpers with comparable speed, friendlier error handling, and are easier to understand than most usual stream code.
Helpers
map(mapFn, iterable)
filter(filterFn, iterable)
flatten(iterable)
take(size, iterable)
drop(size, iterable)
slice(start, end, iterable)
tap(tapFn, iterable)
batch(size, iterable)
filter(filterFn, iterable)
collect(iterable)
consume(iterable)
All helpers are curried if needed to help with composition.
Map
Map a function or async function over an iterable.
const { map } = require('aih')
async function * generate() {
for (let i = 0; i < 9; i++) {
yield i;
}
}
// Fake node stream (could be mongo cursor / fs file, ...)
const stream = Readable.from(generate());
const getItem = map(x => x + 1)(stream);
async function test() {
for await (item of getItem) {
console.log(item); //2, 3, 4, ...
}
}
test();
Filter
Filter over an iterable
const { Readable } = require('stream');
const { filter } = require('aih')
async function * generate() {
yield {
name: 'guest1',
type: 'guest',
};
yield {
name: 'admin1',
type: 'admin',
};
yield {
name: 'admin2',
type: 'admin'
};
}
// Fake node stream (could be mongo cursor / fs file, ...)
const randomUser = Readable.from(generate());
const filterUser = filter(({ type }) => type === 'admin')(randomUser);
async function test() {
for await (user of filterUser) {
console.log(user);
}
}
test();
Flatten
Flatten an iterable.
const { flatten } = require('aih')
async function * generate() {
for (let i = 0; i < 9; i++) {
yield [i, i + 1];
}
}
// Fake node stream (could be mongo cursor / fs file, ...)
const stream = Readable.from(generate());
const flattenedStream = flatten(stream);
async function test() {
for await (item of flattenedStream) {
console.log(item); //1, 2, 2, 3, 3, 4,...
}
}
test();
Take
Take a number of item from an iterable
const {
take,
collect,
} = require('aih')
async function * generate() {
yield {
name: 'guest1',
type: 'guest',
};
yield {
name: 'admin1',
type: 'admin',
};
yield {
name: 'admin2',
type: 'admin'
};
}
const randomUser = generate();
async function test() {
const result = await collect(take(1, randomUser));
console.log(result);
// [ { name: 'guest1', type: 'guest' } ]
}
test()
Drop
const {
drop,
collect,
} = require('aih')
async function * generate() {
yield {
name: 'guest1',
type: 'guest',
};
yield {
name: 'admin1',
type: 'admin',
};
yield {
name: 'admin2',
type: 'admin'
};
}
const randomUser = generate();
async function test() {
const result = await collect(drop(2, randomUser));
console.log(result);
// [ { name: 'admin2', type: 'admin' } ]
}
test()
Slice
const {
slice,
collect,
} = require('aih')
async function * generate() {
yield {
name: 'guest1',
type: 'guest',
};
yield {
name: 'admin1',
type: 'admin',
};
yield {
name: 'admin2',
type: 'admin'
};
}
const randomUser = generate();
async function test() {
const result = await collect(slice(1, 2, randomUser));
console.log(result);
// [ { name: 'admin1', type: 'admin' } ]
}
test()
Tap
const {
tap,
map,
collect
} = require('aih');
const _ = require('lodash/fp);
async function * generate() {
for (let i = 0; i < 9; i++) {
yield i;
}
}
const asyncIterable = generate();
async function test() {
const result = await _.flow(
tap(console.log),
map(x => x * 2),
collect,
)(asyncIterable);
console.log(result);
// 2, 4, 6, 8 ...
}
test()
Batch
const {
batch,
collect,
} = require('aih');
async function * generate() {
for (let i = 0; i < 9; i++) {
yield i;
}
}
const asyncIterable = generate();
async function test() {
const result = await collect(batch(2, asyncIterable));
console.log(result);
// [[1, 2], [3, 4], ...]
}
test();
Collect
Collect values from an iterable
const { Readable } = require('stream');
const { collect } = require('aih')
async function * generate() {
yield {
name: 'guest1',
type: 'guest',
};
yield {
name: 'admin1',
type: 'admin',
};
yield {
name: 'admin2',
type: 'admin'
};
}
// Fake node stream (could be mongo cursor / fs file, ...)
const randomUser = Readable.from(generate());
async function test() {
const users = await collect(randomUser); //array of users
}
test();
Consume
Consume an iterable, useful to treat a pipeline with no values in the end.
const {
tap,
consume,
} = require('aih')
async function * generate() {
yield {
name: 'guest1',
type: 'guest',
};
yield {
name: 'admin1',
type: 'admin',
};
yield {
name: 'admin2',
type: 'admin'
};
}
const randomUser = generate();
async function test() {
await consume(tap(console.log, randomUser));
}
test();