Promise 当做状态机使用

const fn = (num) =>{
	if(num > 2){
		return '数字大于2'
	}
	if(num === undefined){
		return '数字不存在'
	}
	return num
}

Promise 状态机改写:

const fn = (num) =>{
	if(num > 2){
		return Promise.reject('数字大于2')
	}
	if(num === undefined){
		return Promise.reject('数字不存在')
	}
	return Promise.resolve(num)
}

//使用
fn(num).then(res => {message.success(res)}).catch(err => message.error(err))

Promise Async 状态机改写:

const fn = async(num) =>{
	if(num > 2){
	 return	Promise.reject('数字大于2')
	}
	if(num === undefined){
	 return	Promise.reject('数字不存在')
	}
	return num
}

Promise Async Throw 状态机改写:

const fn = async(num) =>{
	if(num > 2){
		throw '数字大于2'
	}
	if(num === undefined){
		throw '数字不存在'
	}
	return num
}