通过a标签download和href实现下载文件

下载只能是同源下载

<input id='file' type='file' />

const file = document.querySelector('#file')
file.onChange = function (e) {
    const file = e.target.files[0]
    const aLink = document.createElement('a')
    a.serAttribute('download', 'abc.html')
    a.href = URL.createObjectURL(file) // or new File
    a.click()
}

文件预览

const img = new Image()
const fileRead = new FileReader()
fileRead.onload = function () {
  img.src = fileRead.result
}
fileRead.readAsDataURL(file)