计算一个数的阶乘

Posted 2021-05-29 Jay_帅小伙

迭代

function fn(num){
	if(num <=0){ return undefuned }
	let total = 1
	for(let n = num; n>1; n--){
		total = total * n
	}
	return total
}
fn(4)
//--------------------
function fn(num){
	if(num <=0){ return undefuned }
	let total = 1
	for(let n = 1; n<=num; n++){
		total = total * n
	}
	return total
};
fn(4)

递归

function fn(n){
	if(n<0){return 'undefined'}
	if(n===0){return 0}
	if(n===1){return 1}
	return n * fn(n - 1)
}
fn(5)//120