➢ Ten Functions

"Ten Functions" is a prepared environment for practicing introductory function writing with automated tests for feedback.

Setup Instructions

1. Clone this project

   git clone THIS_REPOSITORY_URL ~/IdeaProjects/ten-functions
   

   Replacing THIS_REPOSITORY_URL with the clone url of this repository. The clone url can be found by clicking on the green "Code" button. Make sure you are using the SSH remote; the url should start with git@github.com, not https://. If the url starts with https://, click the button in the top right of the dialog that says "Use SSH".

2. Open up the project with your IDE.

3. Write your javascript code for the problems described below in solutions.js.

4. Open up index.html in your web browser to see the test results.

Workflow

1. At first, all of the test results will be red and failing, as you haven't written any code in solutions.js yet.

2. Inside of solutions.js write code that creates the functions detailed in the section below.

3. As you make changes to the code in solutions.js, refresh the index.html page in your browser.

4. Observe how the test results change as you update your functions code.

5. Read the output from the failing tests to help you figure out what changes you need to make to solutions.js.

The "Ten Functions" Exercises

0. The comments to the right of the function call example demonstrate the output of the function's operation on the provided input(s). Add your function definitions to solutions.js. Refresh index.html to run automated tests for feedback on your solutions.

1. Define a function named isTrue that takes in any input and returns true if the input provided is exactly equal to true in value and data type.

    isTrue(true)             // true
    isTrue(false)            // false
    isTrue(0)                // false
    isTrue(null)             // false
    isTrue("true")           // false
    isTrue("Banana")         // false
    isTrue([1, 2])           // false
   

2. Define a function named isFalse that takes in a value and returns a true if and only if the provided input is equal to false in both type and value.

    isFalse(false)             // true
    isFalse(true)              // false
    isFalse(0)                 // false
    isFalse(null)              // false
    isFalse("")                // false
    isFalse("Banana")          // false
    isFalse([1, 2])            // false
   

3. Define a function named not that takes in any input and returns the boolean opposite of the provided input.

    not(false)                  // true
    not(0)                      // true
    not("")                     // true
    not(null)                   // true
    not(NaN)                    // true
    not(undefined)              // true
    not(true)                   // false
    not("something")            // false
    not(Infinity)               // false
    not(123)                    // false
   

4. Define a function named addOne that takes in a single input. If the input is a number or a numeric string, return the value plus one.

    addOne(0)                    // 1
    addOne(2)                    // 3
    addOne(-5)                   // -4
    addOne(5.789)                // 6.789
    addOne(Infinity)             // Infinity
    addOne("2")                  // 3
    addOne("0")                  // 1
    addOne("banana")             // NaN
    addOne(true)                 // NaN
    addOne(NaN)                  // NaN
   

5. Define a function named isEven that takes in a single input. If the input is an even number or a string containing an even number, return true. Any other input should return false for the output.

    isEven(2)                   // true
    isEven(-8)                  // true
    isEven(0)                   // true
    isEven("42")                // true
    isEven(1)                   // false
    isEven("-3")                // false
    isEven(false)               // false
    isEven("banana")            // false
   

6. Define a function named isIdentical that takes in two input arguments. If each input is equal both in data type and in value, then return true. If the values are not the same data type or not the same value, return false.

    isIdentical(3, 3)                     // true
    isIdentical(false, false)             // true
    isIdentical("hello", "hello")         // true
    isIdentical(3, 3.0)                   // true
    isIdentical(undefined, undefined)     // true
    isIdentical(2, "2")                   // false
    isIdentical("javascript", "java")     // false
   

7. Define a function named isEqual that takes in two input arguments. If each argument is equal only in value, then return true. Otherwise return false.

    isEqual(3, "3")                       // true
    isEqual("abc123", "abc123")           // true
    isEqual(true, 1)                      // true
    isEqual(0, false)                     // true
    isEqual(4, -5)                        // false
    isEqual("java", "javascript")         // false
   

8. Define a function named or that takes in two input arguments. The output returned should be the result of an or operation on both inputs.

    or(true, true)                    // true
    or(true, false)                   // true
    or(false, true)                   // true
    or(false, false)                  // false
    or("hello", "world")              // "hello" (this behavior is non-obvious, research more!)
   

9. Define a function named and that takes in two input arguments and returns the result of a logical and operation of both inputs.

    and(true, true)                    // true
    and(true, false)                   // false
    and(false, true)                   // false
    and(false, false)                  // false
    and("hello", "world")              // "world" (this behavior is non-obvious, research more)
   

10. Define a function named concat that takes in two input arguments. If both arguments are strings, then return the concatenated result. If two numbers are provided, then return the string concatenation of each set of numerals.

    concat("code", "up")                // "codeup"
    concat("connect", 4)                // "connect4"
    concat("hello", "world")            // "helloworld"
    concat(4, 2)                        // "42"
    concat(true, true)                  // "truetrue"
    

Hints

Consider this example problem.

Write a function called isBoolean that takes in a value and returns a boolean if the argument provided is a boolean value or not.

• isBoolean("Dog") should return false because a string is not a boolean
• isBoolean(false) should return true because only true and false are boolean values.
• When a problem says return, it means return, not console.log.
• When a problem says that a function will take in an input, then it means the function must be defined so that it takes in an argument as its input, rather than relying on variables defined outside the function.

The following example is incorrect because the function does not take in an argument. It's referencing a global variable, and that is not the same as accepting an input as an argument.

var input = "Grace Hopper"
function isBoolean() {
    return typeof input == "boolean";
}

This is incorrect because the function doesn't return the output. Functions that do not have an explicit return statement return undefined by default.

function isBoolean(input) {
    console.log(typeof input == 'boolean');
}

Correct solution:

function isBoolean(input) {
    return typeof input == "boolean";
}

About

• Testing framework: Jasmine
• "Ten Functions" Originally Made by Ryan Orsinger, adapted for use at Codeup