Recursion

Question 1

What is “recursion?”

Answer 1

calling a function on itself

Question 2

What is a “factorial”

Answer 2

to take a factorial of a number, you multiply that number by each number between itself and one. So the factorial of 5 is equal to 5 * 4 * 3 * 2 * 1, or 120.

Question 3

what is the “base case?”

Answer 3

this is a statement, usually within a conditional clause like if, that stops the recursion. If you don’t have a base case, the recursion will go on infinitely and your program will crash

Question 4

What is a “termination condition?”

Answer 4

a statement that will cancel recursion in the event of bad input or other potential error.

Question 5

How to build your recursive case (the code that will be repeated)

Answer 5

ensure that the arguments you use for the recursion will lead to your base case

Question 6

factorial example (at the bottom show how the factorial runs through the base case)

Answer 6

function factorial(n) {

  // termination condition
  if(n  0){
      return n * factorial(n - 1);
  };
}

//show how the factorial runs:
return n * (n-1) * (n-1-1) * (n-1-1-1)...

Question 7

where is the data stored while you are running a function?

Answer 7

When you run a program, the data that is produced within that program (variables, function calls, etc.) are stored in the stack, which you can think of as a temporary storage device for the computer.

Every time a function is called within a program, the returned value of that function is stored in the stack.

Question 8

another factorial example

Answer 8

// Create an empty array called "stack"
var stack = [];
// Here is our recursive function
function power(base, exponent) {
  // Base case 
  if ( exponent === 0 ) {
    return 1;
  }
  // Recursive case
  else {
	stack[exponent - 1] = base * power(base, exponent - 1);
    return stack[exponent - 1];
  }
}

//show how the factorial runs
//base * base * base (through the number of times it takes for exponent to