Reverse / Sort

reverse()

• Destructive function which reverses the order of elements in an existing array.

let arr = [1,2,3];
arr.reverse();

arr; // [ 3, 2, 1 ]

sort()

• The sort() function's default behavior is to evaluate a provided array and rearrange the elements destructively into order determined by value.

let numArr = [4,5,1,7,19,5,3,7];
numArr.sort();

numArr; // [ 1, 19, 3, 4, 5, 5, 7, 7 ]

let strArr = ['coconut', 'peach', 'banana', 'xylophone', 'apple'];
strArr.sort();

strArr; // [ 'apple', 'banana', 'coconut', 'peach', 'xylophone' ]

• sort()s default behavior has its shortcomings (as is noticeable in the numArr example above). Luckily, we can provide a sort function as an argument and customize how the sort algorithm works.
• provide an anonymous (or named) function as an argument (sort(function(a,b){})).

• the arguments (a, b) provided to the anonymous function will represent the elements of the array being evaluated. If the values are equal, a 0 will be returned, representing equality. Otherwise, the return value will be either > 0 or < 0, illustrating that the value is greater than or less than what it is being evaluated against. The sort() function will take this input to order the elements as it evaluates them.

  let stdSort = [4,111,19,16,5,1009,56,78,15];
  stdSort.sort();
  stdSort; // [ 1009, 111, 15, 16, 19, 4, 5, 56, 78 ]
  
  let customSort = [4,111,19,16,5,1009,56,78,15];
  customSort.sort(function(a,b) {
      return a-b;
  });
  customSort; // [ 4, 5, 15, 16, 19, 56, 78, 111, 1009 ]
  
  //\\//\\ You can reverse the sort order by reversing the evaluation order//\\//\\
  
  let customSort2 = [4,111,19,16,5,1009,56,78,15];
  customSort2.sort(function(a,b) {
      return b-a;
  });
  customSort2; // [ 1009, 111, 78, 56, 19, 16, 15, 5, 4 ]
  
  //\\//\\//\\ Cases may arise in which you will need to create a custom comparator:
  let words = ["apple", "Coconut", "Banana", "Apple"]
  
  words.sort(function(a, b) {
    if (a < b) {
      return -1;
    }
    if (a > b) {
      return 1;
    }
    // didn't return yet, names must be equal
    return 0;
  });
  words; // ["Apple", "Banana", "Coconut", "apple"]
  

Skill Drill

1. Create an array of strings containing 3 proper nouns (capitalized first letters) and 3 which are all lowercase, and store it into a variable nouns.

2. Call the reverse function on your nouns variable and print out the array.

3. Use a custom sort to order them in descending order (e.g. from highest ASCII value to lowest).

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