Differences

This shows you the differences between two versions of the page.

--- java-script:reduce:group-people-by-age [2023/08/07 20:31] – odefta
+++ java-script:reduce:group-people-by-age [2023/08/07 20:42] (current) – odefta
@@ Line 1: / Line 1: @@
-====== Use reduce to group people by age ======
+====== Using reduce to group people by age ======
+In this example, the accumulator starts as an empty object {}, and the function is applied to each person object in the people array.
+This function is a neat example of how you can use **reduce** in conjunction with other modern JavaScript features like **destructuring** and the **nullish coalescing operator** to concisely perform a complex transformation on an array.
 <code javascript group-people-by-age-reduce.js>
 function groupPeople(people) {
-    //check if people is an object
     if (people !== null && Array.isArray(people) && Array(people).length !== 0 && typeof people[0] === 'object') {
-        //get all possible ages
         let groupedPeopleByAge = people.reduce((group, person) => {
-            const { age } = person;
+            const { age } = person; //destructuring
-            group[age] = group[age] ?? [];
+            group[age] = group[age] ?? []; //nullish coalescing operatorn
             group[age].push(person.name);
             return group;
@@ Line 29: / Line 32: @@
 let groupedPeopleByAge = groupPeople(people);
 console.log(groupedPeopleByAge);
+</code>
+Output:
+<code>
+{ '25': [ 'Alice', 'Bob', 'Eve' ], '30': [ 'Charlie', 'David' ] }
 </code>