javascript-functions-loops-arrays.js

// Functions Loops and Arrays
// Functions - dynamic and reusable pieces of code; need to be invoked; will always need/have a return -- will return one thing;
// console(log) - dev tool that will allow devs to see the work in progress; user will not see this 
// return - "final product"; 

// EXAMPLE:
// Create a function that will multiply each number in an array by 5.

// pseudocode:
// input: array of numbers
// output: each value multiplied by 5
// create a function named mult5 that will iterate through my array and multiply each value by 5. Return an array with new values.

// ** arrays cannot be multiplied **
const mult5 = (array) => {
  return array * 5
  // the computer sees this as [our array] * 5 but it cannot access what's inside like this
}
// console.log(mult5(firstArray));
// output: NaN

// ** this for loop can now access the array **
const mult5 = (array) => {
  for (let i = 0; i < array.length; i++) {
    console.log(array[i])
    // logs the values of the array
  }
}
// console.log(mult5(firstArray));
// returning undefined because our function is not returning anything yet

const mult5 = (array) => {
  for (let i = 0; i < array.length; i++) {
    console.log(array[i] * 5)
    // logs the values of the array * 5, but it is just a console log. The function is still returning nothing.
  }
}
// console.log(mult5(firstArray));

// ** a return inside of the loop **
const mult5 = (array) => {
  let storageArray = []
  // temporarily hold values we will need later
  for (let i = 0; i < array.length; i++) {
    storageArray.push(array[i] * 5)
    // pushing them into the temporary array
    return storageArray
    // placing our return here will return the first true instance of the loop instead of letting the for loop finish it's iteration.
  }
}
// console.log(mult5(firstArray));
// output: [ 5 ]

var firstArray = [1, 2, 3, 4, 5]
var secondArray = [10, 20, 30, 40, 50]
var thirdArray = [3, 5, 7]

const mult5 = (array) => {
  let storageArray = []
  // temporary array to hold values
  for (let i = 0; i < array.length; i++) {
    // iterate through
    storageArray.push(array[i] * 5)
    // storing the new values inside of our temporary array
  }
  return storageArray
  // return the array with correct output
}

// console.log(mult5(firstArray));
// // output: [ 5, 10, 15, 20, 25 ]
// console.log(mult5(secondArray))
// // [ 50, 100, 150, 200, 250 ]
// console.log(mult5(thirdArray));
// // [ 15, 25, 35 ]
// console.log(mult5([24, 222, 5, 60, 72]));
// // [ 120, 1110, 25, 300, 360 ]

// EXAMPLE:
// Create a function that will take an array of strings and return them in an array with a string saying they have entered the groupchat.

// pseudocode:
// input: array of strings
// output: arrray with strings interpolated
// create a function called iPhone that will take an array of strings, iterate through, and return them string interpolated into a groupchat together.

var contacts = ["Adrian", "Tori", "Shaun", "Mal"]

const iPhone = (array) => {
  let groupChat = []
  // temporary array
  for (let i = 0; i < array.length; i++) {
    groupChat.push(`${array[i]} has now entered the groupchat!`)
    // string interpolation the value in a string
  }
  return groupChat
  // return the groupchat and when the person has entered
}
// console.log(iPhone(contacts))
// [
//   'Adrian has now entered the groupchat!',
//   'Tori has now entered the groupchat!',
//   'Shaun has now entered the groupchat!',
//   'Mal has now entered the groupchat!'
// ]

// EXAMPLE:
// create a function that will take an array and return the even numbers in a new array.

var givenArray = [1, 3, 5, 7, 11, 10, 26, 30, 22]

// pseudocode:
// input: array
// output: array of even numbers
// create a function called onlyEvensEver that will take an array iterate through to only return teh even numbers ... ever

const onlyEvensEver = (array) => {
  let evenNumbers = []
  for (let i = 0; i < array.length; i++) {
    // conditionally render whether it is an even or odd number
    if (array[i] % 2 === 0) {
      evenNumbers.push(array[i])
    }
  }
  return evenNumbers
}
// console.log(onlyEvensEver(givenArray));
// [ 10, 26, 30, 22 ]
// console.log(onlyEvensEver([13, 22, 55, 67, 59,]));