SOURCE

// 延时封装
function delay(ms) {
    return new Promise(resolve => setTimeout(resolve, ms))
}

async function processWithConcurrency(tasks, concurrencyLimit) {
    const results = []
    const excuting = new Set()
    for (const task of tasks) {
        const taskResponse = Promise.resolve().then(() => {
            task()
        })
        results.push(taskResponse)
        if (concurrencyLimit <= tasks.length) {
            const e = taskResponse.then(() => excuting.delete(e))
            excuting.add(e)
            if (excuting.size >= concurrencyLimit) {
                await Promise.race(excuting)
            }
        }
    }
    return Promise.all(results)
}

// 执行
async function fetchApiData(url) {
    await delay(1000)
    return `response from ${url}`
}

const urls = [
    'https://examp1.api.com',
    'https://examp2.api.com'
]

const tasks = urls.map(url => {
    return () => {
        fetchApiData(url)
    }
})

processWithConcurrency(tasks, 2).then(results => {
    // console.log(results)
})