arraydrills.js

arraydrills.js

1.) Creating arrays
//function with 3 arguments, item1,item2,item3
//return three items as an array
function makeList(item1,item2,item3) { 
  return [item1,item2,item3];
} 

2.) Adding array items
//function called addToList that accepts an array and an item as arguments, and returns the
//array with the item added to the end. Function will have side effect of changing original array. 
function addToList (list, item) {
  list.push(item)
  return list
} 

3.) Accessing array items
//2 functions: accessFirstItem(array), and accessThirdItem(array)
//Both functions take single argument, an array of values called array
//accessFirstItem returm 1st item in array
//acccessThirdItem return 3rd item in array 

function accessFirstItem(array){
  var items = array[0];
  return array[0];
} 
function acccessThirdItem(array){
  var items = array[2];
  return array[2];
} 


4.) Array length and access
//2 functions: findLength and accessLastItem 
//Both functions take 1 argument: an array of values
//findLength return length of array
//accessLastItem return last value in array without changing array
function findLength(array) {
  return array.length
} 
function accessLastItem (array) {
  var items = array[4];
  return array[4];
} 

5.) Array copying I 
//2 functions firstFourItems, and lastThreeItems
//both functions take a single argument: an array of values called array (Includes at least 5 values, maybe more)
//firsrFourItems print first four items in array
//lastThreeItems print last three items in array
function firstFourItems(array){
  return array.slice(0);
}
function lastFourItems(array){
  return array.slice(-3);
}

6.) Array copying II 
//2 functions, minusLastItem, and copyFirstHalf
//1 argument, an array of values called array
//minusLastItem, copy entire array except last item
//copyFirstHalf, return array that copies first half
//copyFirstHalf should return smaller half if there are uneven numbers
function minusLastItem(array){
  return array.slice(0,array.length));
} 
function copyFirstHalf(array){
  return array.slice(0,array.length/2));
} 
//question:why use .slice method? 

7.) Squares with map 
//function named squares
//takes 1 argument, array of values called array
//function should return a new array with the square value from the original array
//no loop, MUST use .map method 
function squares(array) { 
  var numbers= array
  var roots= numbers.map(function(x){
    return x*2;
  }); 
  
  function squares(array){
    var doubles.array.map(function(num){
      return num**2;
    });
    return doubles;
  }
  
  8.) Sort
  //function greatestToLeast
  //takes 1 argument:array
  //function return array with sorted numbers greatest to least
  function greatestToLeast(array){
    return array.sort(function(a,b){
      return b-a;
    }); 
  }
  
  9.) Filter
  //function shortWords
  //1 argument:an array of strings called array
  //function should return an array with strings that are shorter than 5 characters
  //use .filter method 
  
 function shortWords(array){
   return array <= 6;
   var filtered = array.filter(shortWords);
   return function shortWords 
   
   function shortWords(array){
     return array.filter(function(word){
       return word.length<5;
     });
   }
   
   10.) Find
   //function divisibleBy5
   //1 argument, array of numbers called array
   //function should return 1st value in array that is divisible by 5. Not divisible by 5, return undefined
   //Use .find method 
   //*COULD ALSO POSSIBLY USE FOR LOOP TO SOLVE PROBLEM*
   function divisibleBy5(array){
     return array.find(function(num){
       return num % 5 == 0; 
     });
   }