Functions

Question 1

Create a function named ‘arrayCounter’ that takes in a parameter which is an array. The function must return the length of an array passed in or 0 if a ‘string’, ‘number’ or ‘undefined’ value is passed in.

Answer 1

function arrayCounter(array) {
  if (typeof array === "string" || typeof array === "number" || typeof array === "undefined"){
    return 0;
  } else {
    return array.length;
  }
};

Question 2

var x = 1;
var y = 1;

function hypotenuse(a , b) {
  var cSquared = a * a + b * b;
  x = Math.sqrt(cSquared);
  return x;
}

hypotenuse(x, y);

When the ‘hypotenuse’ function is called the value of ‘x’ changes from 1. Fix it so that ‘x’ is still 1 in the global scope.

Answer 2

var x = 1;
var y = 1;

function hypotenuse(a , b) {
  var cSquared = a * a + b * b;
  var x = Math.sqrt(cSquared);
  return x;
}

hypotenuse(x, y);

Question 3

var anonymousFunction;

Set the variable ‘anonymousFunction’ to be an anonymous function without any code to be executed.

Answer 3

var anonymousFunction = function(){};

Question 4

(function () {
window.didExecute = true;
});

Make the anonymous function with the code ‘window.didExecute = true’ execute.

Answer 4

(function () {
window.didExecute = true;
})();

Question 5

Aside from providing the return value to the code that called the function, what other behavior does return have that is useful?

Answer 5

it stops execution of the function immediately

Question 6

In the following code, what will be output by the console.log call?

 function example ( ) {
  var color = "red";
  return color;
}

example(“blue”);

console.log(color);

Answer 6

An error is thrown, color is not defined

Question 7

Given the following code snippet, what are the values of a and b inside of the function when it is called?

 function example (a, b) {
  console.log("a === ", a,  " , b === ", b);
}

example(“Treehouse”);

Answer 7

a === “Treehouse”, b === undefined

Question 8

When the return statement is called without a value, what is the value returned from the function?

Answer 8

undefined

Question 9

Why are functions so important, especially in the browser?

Answer 9

it allows you to attach code to be executed when events like clicks and key-presses happen

Question 10

What is an anonymous function?

Answer 10

it is a function declared without a name that can be stored in a variable, passed as a value, or invoked immediately

Question 11

In the following code, what value will be printed to the console?

var animal = “cow”;

function display (animal) {
  console.log(animal)
}

animal = “pig”

display(“horse”);

Answer 11

“horse”

Question 12

What happens when a function is called with fewer arguments than are defined in the function?

Answer 12

any remaining arguments hold the value undefined

Question 13

Why is it a common pattern to execute anonymous functions immediately in your program?

Answer 13

functions provide a new variable scope, so variables can be used privately and without collisions