In other words, if you create a function called add, you call the add function inside the add function.
Once again,
function add(){
add();
}
Same as above. ^^
This example uses the factorial in mathematics as an example.
There are some people who have a headache because of sudden math.
I can't see this course because I don't know what factorial is. Some people may have to go out.
Do not worry.
5! If you write like this and solve 5 !, 5 * 4 * 3 * 2 * 1, so 120 is the answer.
This is how we learned what factorial is.
Then 10! What is this?
10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1 ^-^ * The answer is 4,939,200.
So let's look at a recursive function that calls its own function inside a function.
By the way, this recursive function is a bit confusing if I understand and explain properly, but it is hard to find the data with the flow chart.
The source is:
function factorial(fnum){
end_num = 1;
if(fnum == end_num) return end_num;
else return fnum*factorial(fnum-1);
}
document.write(factorial(3));
document.write(factorial(3));
The function call is sending parameter 3 with the output statement.
function factorial(fnum){
end_num = 1;
if(fnum == end_num) return end_num;
else return fnum*factorial(fnum-1);
}
document.write(factorial(3));
fnum, a parameter of factroial, has a value of 3. Therefore, fnum = 3.
end_num = 1;
Factorial multiplies until its number is one. Therefore, because end number is 1, declare end_num = 1.
if(fnum == end_num) return end_num;
The end_num value is 1 and fnum is 3. If fnum is 1, end_num is returned.
else return fnum*factorial(fnum-1);
Returns fnum * factroial (fnum-1). If fnum is 3,
Is to return 3 * factorial (2). So this part will go to the function call part?
However, since the value is passed but there is a call statement, factroial (2), the function is called to make 2 the value of the parameter, meets the else statement, and returns 2 * factorial (1).
If so, the factorial (3) statement is 3 * 2 * factorial (1). factorial (1) is called to return 1 because it is equal to end_num
The call statement will receive 3 * 2 * 1 as output. Do you understand? ^^
I don't think so but I'll explain it again.
Execute function call factorial (3)
fnum becomes 3 and 3 * factorial (2) is returned by else statement.
In 3 * factorial (2), factorial (2) is a function call and the parameter value is 2, so it meets the else statement and returns 2 * factrorial (1) and calls 1 as the parameter value.
Because end_num and fnum match, it meets the if statement and returns 1,
The function will return 3 * 2 * 1. ^^
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>JavaScript</title>
<script>
function factorial(fnum){
end_num = 1;
if(fnum==end_num) return end_num;
else return fnum*factorial(fnum-1);
}
document.write("!="+factorial(3));
</script>
</head>
<body>
</body>
</html>
This concludes the description of recursive functions. ^^
Thank you for visiting. If you have any inquiry or explanation of mistakes, please use the comments below.
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