1. 动态引入 polyfill

function scriptLoader(url) {
       return new Promise((resolve,reject)=>{
          var head = document.getElementsByTagName('head')[0];
          var script = document.createElement('script');
          script.type= 'text/javascript';
          script.onload = ()=>resolve()
          script.src = src;
          head.appendChild(script);
       })
}
// 注: 若要适配 ie, 需添加 state. onreadystatechange 事件

2. axios 发送 post 请求(json+file) 节选自github

var formdata = new FormData()
for (var pk in this.formItem) {
    formdata.set(pk, this.formItem[pk])
}
formdata.set('file', this.file, this.file.name)
/* set和append区别
formData.set('a', 5)
formData.set('a', 6) //  {a: 6}
formData.append('b', 5)
formData.append('b', 6) // {b: [5, 6]} */
axios({
    method: 'post',
    url: '//k-on.live:8081/api/std/submit',
    headers: {
        'Content-Type': 'multipart/form-data;chaset=UFT-8'
    },
    data: formdata,
    onUploadProgress: progressEvent => { this.loading = progressEvent.loaded / progressEvent.total }
}).then(config => {
    let { data } = config
    if (data.success) {
        this.$Modal.success({ content: data.message });
    } else {
        this.$Modal.warning({ content: data.message });
    }
}).catch(() => {
    this.$Modal.warning({ content: '网络错误，请重试' });
}).then(() => {
    this.loading = 0
})

3. 原生 xhr mdn掘金

3.1 普通 GET 请求拿 json

3.2 普通 GET 请求拿文件

3.3 POST 请求传 json

3.4 文件上传

let btn = document.querySelector('#btn')
let file = document.querySelector('#file')
btn.onclick =  () => file.click() // 调取系统选择图片的弹框
// 监听input的file变化值
file.onchange = function (event) {
    let file = event.target.files[0]
    upload(file)
}
function upload(file) {
    let xhr = new XMLHttpRequest()
    xhr.open('post', '/upload', true)
    let formData = new FormData()
    formData.set('filename', file)
    xhr.send(formData)
    xhr.onreadystatechange = function() {
        if (xhr.readyState === 4 && xhr.status === 200) {
            alert('success')
        } 
    }
}