promise-concurrency.js

require('console-stamp')(console, '[HH:MM:ss.l]')

const request = require('request')


const categories = [4754, 4755, 4756, 4635, 4634, 4620, 4892, 4621, 4622]


function getData(id) {
    console.log("Started fetching courses in category " + id)
    let url = `https://www.genshuixue.com/sapi/channel/list?topChannelId=${id}&secondChannelId=${id}&thirdChannelId=all`
    return new Promise((resolve, reject) => {
        request(url, (error, response, body) => {
            if (error) reject(error)
            if (response.statusCode != 200) {
                reject(`Response error, status code=<${response.statusCode}>`)
            }
            resolve(JSON.parse(body))
        })
    })
}


categories.forEach(function (value, index) {
    getData(value).then((result) => {
        total = result.data.pager.total
        console.log("Completed id=" + value + " and fetched " + total + " courses")
    })
})

Running result:

❯ node promise-concurrency.js
[[23:35:55.018]] [LOG]    Started fetching courses in category 4754
[[23:35:55.023]] [LOG]    Started fetching courses in category 4755
[[23:35:55.023]] [LOG]    Started fetching courses in category 4756
[[23:35:55.024]] [LOG]    Started fetching courses in category 4635
[[23:35:55.024]] [LOG]    Started fetching courses in category 4634
[[23:35:55.024]] [LOG]    Started fetching courses in category 4620
[[23:35:55.024]] [LOG]    Started fetching courses in category 4892
[[23:35:55.024]] [LOG]    Started fetching courses in category 4621
[[23:35:55.025]] [LOG]    Started fetching courses in category 4622
[[23:35:55.285]] [LOG]    Completed id=4620 and fetched 8 courses
[[23:35:55.295]] [LOG]    Completed id=4635 and fetched 9 courses
[[23:35:55.360]] [LOG]    Completed id=4634 and fetched 2 courses
[[23:35:55.371]] [LOG]    Completed id=4621 and fetched 9 courses
[[23:35:55.447]] [LOG]    Completed id=4755 and fetched 29 courses
[[23:35:55.451]] [LOG]    Completed id=4754 and fetched 3 courses
[[23:35:55.462]] [LOG]    Completed id=4756 and fetched 27 courses
[[23:35:55.465]] [LOG]    Completed id=4892 and fetched 19 courses
[[23:35:55.671]] [LOG]    Completed id=4622 and fetched 23 courses