Function Basics

Example 1 (Triple Number)

Here is a function where the input is a number (primitive) and the output is a number.

This function simply triples the input, and returns the result

//Outputs the triple of input x
let tripleNumFct = (x) => 3 * x

//Try It
let x = 10;
let y = tripleNumFct(x);
println(y);

Example 2 (Square Number)

We assign it to a var myFct and then call myFct.

(x) = function input params
x*x = function operation

// Assigns function to var myFct */
let myFct = (x) => x*x;

//Try It
let result = myFct(3);
println('Square of 3: ' + result);

Example 3 (getFirst - Object Input)

Here is a function where the input is an object (an array) and the output is an element from the array.

This function returns the first element in the input array.

let getFirstFct = (array) => array.get(0);

let array = ['A++', 'A', 'A-'];
let result = getFirstFct(array);
println('Result is ' + result);

Example 1 (Max)

Simple function to return max of three numbers.

// Returns max of three numbers
let maxFct = (a, b, c) => {
	let max = (a >= b) ? a : b;
	return (max >= c) ? max : c;
}

//Try It
let a = 2;
let b = 11;
let c = 3;
println(maxFct(a, b, c));

Example 2 (Print Array)

Here is a function that simply prints the elements in a list.

//Prints a list/array
let fct = (list) => {
	for (let nextElem of list) {
		println(nextElem);
	}
}

//Try It
let names = ['Asha', 'Chin', 'Kofi', 'Chin'];
fct(names);

Example 3 (Sum Array)

Here is a function that returns the sum of the numbers in a list.

//Sums the numbers in a list/array
let fct = (list) => {
	let sum = 0;
	for (let nextElem of list) {
		sum += nextElem;
	}
	return sum;
}

//Try It
let numbers = [10, 20, 30, 40];
let sum = fct(numbers);
println("Sum of list is: " + sum);

Example 4 (Count Evens)

Here is a function that returns a count of the even numbers in a list.

//Function that returns true if num is even
let isEvenFct = (num) => num % 2 == 0;

//Counts the even numbers in a list/array
let fct = (list) => {
	let count = 0;
	for (let nextElem of list) {
		if (isEvenFct(nextElem))
			count++;
	}
	return count;
}

//Try It
let numbers = [7, 8, 9, 10];
let result = fct(numbers);
println("Even Count: " + result);

Example 5 (Factorial)

Simple function to return max of three numbers.

// Returns factorial of param num
let factorialFct = (num) => {
	let result = 1;
	let x = num;
	for (let x = num; x > 1; x--)
		result *= x;
	return result;
}

//Try It
println('Factorial of 2: ' + factorialFct(2));
println('Factorial of 3: ' + factorialFct(3));
println('Factorial of 4: ' + factorialFct(4));

Example 6 (Find First Index)

Here is a function that searches for the param searchValue in a list and returns the index of the first match.

// Returns index of first match (of searchValue in list)
let findFirstIndex = (list, searchValue) => {
	for (let index = 0; index < list.size(); index++) {
		let nextElem = list.get(index);
		if (nextElem.equals(searchValue))
			return index;
	}
	return -1;
}

//Try It
let names = ['Asha', 'Chin', 'Kofi', 'Chin'];
let nm = 'Chin';
let firstIndex = findFirstIndex(names, nm);
println(firstIndex);

Example 7 (Is Prime?)

Here we code a function that tests if a number is prime

let isPrime = (num) => {
	if (num == 1) return false;
	if (num == 2) return true;
	if (num % 2 == 0) return false;
	//3, 5, 7
	if (num <= 7) return true;
	for (let f = 3; f <= 7; f += 2)
		if (num % f == 0)
			return false;
	let max = Math.floor(Math.sqrt(num));
	//From 5, prime factors are 6k+/-1
	let z = 6;
	max++;	//to include 6k-1let isPrime = (num) => {
	while (z <= max) {
		if ((num % (z-1) == 0) || (num % (z+1) == 0))
			return false;
		z += 6;
	}
	return true;
}

//Try It
println("is Prime (37): " + isPrime(37));
//test, expect 25 between 1-100
let count = 1; //count "2"
for (let n = 3; n < 100; n += 2)
	if (isPrime(n))
		count++;
println("Prime count (1-100): " + count);
//test, expect 168 between 1-1000
count = 1; //count "2"
for (let n = 3; n < 1000; n += 2)
	if (isPrime(n))
		count++;
println("Prime count (1-1000): " + count);
println("\nList primes 1-100");
for (let n = 3; n < 100; n += 2)
	if (isPrime(n))
		println("Prime: " + n);