Recursion on Javascript

Question

I want to know how the recursion works in Javascript. I take an example below:

function abc(n){
     document.write(n + "<br>");
     if (n < 4){
         abc(n+1);
         document.write(n + "<br>");
     }
}

My attention is at the 5th line. When will the 5th be executed? Is the 5th line executed before or after the recursion?

Thanks.

The write instruction is located after the recursive function call, hence the execution will take place after the recursive call ;-) — Eineki
– Eineki, Commented May 16, 2017 at 11:05
In javascript, recursion works the same as in any other imperative programming lagnuage. To find out in which order the statements are executed, you can try it out or think about an example. — Aloso
– Aloso, Commented May 16, 2017 at 11:07

Weedoze · Accepted Answer · 2017-05-16 11:03:40Z

3

It will be executed after the recursion

function abc(n){
     document.write(n + "<br>");
     if (n < 4){
         abc(n+1);
         document.write(n + " Foo<br>");
     }
}

abc(1)

answered May 16, 2017 at 11:03

Weedoze

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3 Comments

billyhalim25 Over a year ago

Is it executed after ALL recursion or after the first recusion?

Weedoze Over a year ago

@billyhalim25 You can run the code snippet. You will see that it will display all iteration from 1 to 4. Then it will display the numbers with foo

billyhalim25 Over a year ago

Yes, I understand. But how do the program remember the value for n in document.write(n + " Foo<br>"); as these lines are queued until all recursion finished?

Nina Scholz · Accepted Answer · 2017-05-16 11:25:56Z

2

It is executed aber the first finished recursion. It follows the Depth-first search principle.

    levels                 comment
-------------  ----------------------------------
1
    2
        3
            4  end of recursion calls, max depth
        3
    2
1

function abc(n){
     document.write(n + "<br>");
     if (n < 4){
         abc(n+1);
         document.write(n + "<br>");
     }
}

abc(0);

edited May 16, 2017 at 11:25

answered May 16, 2017 at 11:06

Nina Scholz

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Comments

Adrian Makowski · Accepted Answer · 2017-05-16 11:12:34Z

1

It will be executed after recursion. Recursion invokes functions in functions until conditions are met. In your case variable n should be less than 4 for recursion to go into "deeper" level of function.

abc(1) -> abc(2) -> abc(3)

So you will have 3 synchronous function invocations before program can go to other lines.

answered May 16, 2017 at 11:12

Adrian Makowski

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