3.1. Minimum

The previous chapter introduced the standard function Math.min that returns its smallest argument. We can do that ourselves now. Write a function min that takes two arguments and returns their minimum.

My solution:

function min (a, b) {
      if (a<b) return a;
      else return b;
      }
console.log(min(1,-20));

3.2. Recursion

We’ve seen that % (the remainder operator) can be used to test whether a number is even or odd by using % 2 to check whether it’s divisible by two. Here’s another way to define whether a positive whole number is even or odd:

• Zero is even.

• One is odd.

• For any other number N, its evenness is the same as N - 2.

Define a recursive function isEven corresponding to this description. The function should accept a number parameter and return a Boolean.

Test it on 50 and 75. See how it behaves on -1. Why? Can you think of a way to fix this?

My solution:

function isEven (number) {
	if (number<0) number *= -1;
	if (number == 0) return true;
	else if (number == 1) return false;
	else return isEven (number-2);
}                              
console.log(isEven(-1))

3.3. Bean counting

You can get the Nth character, or letter, from a string by writing “string”.charAt(N), similar to how you get its length with “s”.length. The returned value will be a string containing only one character (for example, “b”). The first character has position zero, which causes the last one to be found at position string.length - 1. In other words, a two-character string has length 2, and its characters have positions 0 and 1.

Write a function countBs that takes a string as its only argument and returns a number that indicates how many uppercase ‘B’ characters are in the string.

Next, write a function called countChar that behaves like countBs, except it takes a second argument that indicates the character that is to be counted (rather than counting only uppercase ‘B’ characters). Rewrite countBs to make use of this new function.

My solution:

var input = "Boo! By the way, if two witches would watch two watches, which witch would watch which watch? Also, a Quick Brown Fox Jumped Over A Lazy Dog! Bye, B";

function countBs(str) {
	var counter = 0;
	for (i=0; i<str.length; i++)
	if (str.charAt(i) == "B") counter += 1;
	return counter;
}

function countChars(str, char) {
	 var counter = 0;
	for (i=0; i<str.length; i++)
	if (str.charAt(i) == char) counter += 1;
	return counter;
}

console.log(countBs(input))
console.log(countChars(input, "w"))
console.log(countChars(input, "h"))