Recipes

Network Request

Make a cancellable network request

interruptible method will be used because fetch interface supports immediate cancellation of the request

Using fetch and AbortController

const { interruptible } = require('no-thanks')

const controller = new AbortController()

const request = interruptible(() =>
    fetch({
        signal: controller.signal,
        /* other request options */
    }), () => controller.abort())()

or without closure

const { interruptible } = require('no-thanks')

const request = interruptible(async grain => {
    const controller = grain(new AbortController())
    return await fetch({
        signal: controller.signal,
        /* other request options */
    })
}, controller => controller != null && controller.abort())

General Purpose Request Function

It's the same request but it takes options as an argument

const { interruptible } = require('no-thanks')

const request = interruptible(async (grain, url, options = {}) => {
    const controller = grain(new AbortController())
    return await fetch(url, {
        ...options,
        signal: controller.signal,
    })
}, controller => controller != null && controller.abort())

const getCurrentBitcoinPrice = () => request('https://api.bitfinex.com/v1/pubticker/btcusd')
    .then(response => response.json())
    .then(({ last_price }) => last_price)

A few more examples of cancellable requests using jQuery.ajax with jquery >= 1.5.1

const { interruptible } = require('no-thanks')

const request = interruptible(async grain => {
    const request = grain($.ajax({
        /* request options */
    }))
    return request.promise()
}, request => {
    if (request != null) {
        return request.abort()
            .catch(err => {
                if (err.statusText === 'abort')
                    return;

                throw err
            })
    }
})

// request().cancel()

Using jQuery.ajax with jquery <= 1.5

const { interruptible } = require('no-thanks')

const request = interruptible(async grain => {
    return await new Promise((resolve, reject) => grain($.ajax({
        /* request options */
        success: resolve,
        error: (jqXhr, status, errorMessage) => {
            if (status === 'abort') resolve(jqXhr)
            else reject(new Error(errorMessage))
        }
    })))
}, request => { request != null && request.abort() })

Reading Large File

For example let's sum the bytes in a file using nodejs

const fs = require('fs')
const { promisify } = require('util')
const { cancellable } = require('no-thanks')

const open = promisify(fs.open)
const stat = promisify(fs.stat)
const read = promisify(fs.read)

const sum = cancellable(async (grain, filename) => {
    const { blksize, size } = await grain(stat(filename))
    const handle = await grain(open(filename, 'r'))

    let sum = 0
    let offset = 0
    while (offset < size) {
        const buffer = Buffer.alloc(blksize)
        const { bytesRead } = await grain(read(handle, buffer, 0, blksize, offset))
        offset += blksize
        if (bytesRead > 0)
            sum += buffer.reduce((a, b) => a + b, 0)
    }

    return sum
}, (_, handle) => handle != null && handle.close())

sum('dir/some-file.dat')
    .then(sum => console.log(`Sum: ${sum}`))