各位大佬， axios 异步请求，回调函数获取全局变量为空，怎么解决这个问题啊？

export const CompOnent= () => {
let growl

const OnSubmitHandler= () => {
axios.post(url, {
}).then(res => {
const.log(growl)
})
}
return (
<div>
<Growl ref={(el) => growl = el} style={{marginTop: '75px'}}/>
</div>
)
}