ds-algo-study/DS-n-Algos/Recursion/My-Recursion-Prac-Website/Recur-website/AUX_MATERIALS/sandbox/factorial.js

Just experimenting with publishing a package

//  We want to write a function factorial(num) which takes a number
//    and returns the product of all consecutive positive integers up to 
//    the given number. The factorial of zero is equal to 1.
//  This problem must be solved recursively.


// Repeating pattern
// multiplying by decremented number

// Where does the pattern break
// when the number is zero

// Base Case
// if num === 0

// Recursive Case
// if num > 0

// Recrusive Step
// num * factorial(num -1)


// Website to visualize the call stack for factorial:
//    https://www.cs.usfca.edu/~galles/visualization/RecFact.html


function factorial ( num ) {
    if ( num === 0 ) {
        return 1;
    }

    return num * factorial( num - 1 )
}

console.log( factorial( 4 ) );


// factorial(num);   // 1st frame,   num = ,
// factorial(num);   // 2nd frame,   num = ,
// factorial(num);   // 3rd frame,   num = ,
// factorial(num);   // 4th frame,   num = ,  returns ,    popped off the stack
// 3rd frame,     return from 4th frame = ,    returns ,     popped off the stack
// 2nd frame,     return from 3rd frame = ,    returns ,     popped off the stack
// 1st frame,     return from 2nd frame = ,    returns ,     popped off the stack
// Final return value: