通过创建DOM节点并即时删除的方法实现
const $copy = (val) =>{
console.log(val)
let myInput = document.createElement('input')
myInput.value = val
document.body.appendChild(myInput)
myInput.select()
document.execCommand('Copy')
document.body.removeChild(myInput)
alert(`成功复制 <${val}>`)
}