js_generator_question

js_generator_question.js

function ajax(url, callback) {
    console.log('ajax enter: ', url)
    // 1、创建XMLHttpRequest对象
    var xmlhttp
    if (window.XMLHttpRequest) {
        xmlhttp = new XMLHttpRequest()
    } else { // 兼容早期浏览器
        xmlhttp = new ActiveXObject('Microsoft.XMLHTTP')
    }
    // 2、发送请求
    xmlhttp.open('GET', url, true)
    xmlhttp.send()
    // 3、服务端响应
    xmlhttp.onreadystatechange = function () {
        if (xmlhttp.readyState === 4 && xmlhttp.status === 200) {
            var obj = JSON.parse(xmlhttp.responseText)
            // console.log(obj)
            callback(obj)
        }
    }
    console.log('ajax leave: ', url)
}

function request(url) {
    console.log('request enter, url: ', url)
    ajax(url, res => {
        console.log('callback enter, url: ', url)
        getData.next(res)
        console.log('callback leave, url: ', url)
    })
    console.log('request leave, url: ', url)
}

function* gen() {
    let res1 = yield request('http://www.httpbin.org/get?q=test1')
    console.log('res1: ', res1)
    let res2 = yield request('http://www.httpbin.org/get?q=test2')
    console.log('res2: ', res2)
    let res3 = yield request('http://www.httpbin.org/get?q=test3')
    console.log('res3: ', res3)
}
let getData = gen()
getData.next()