More Examples for Reduce

Here are some more examples of using the .reduce() function in smart ways with JavaScript:

1. Finding the maximum value in an array:

const numbers = [1, 5, 2, 9, 3];
const max = numbers.reduce((prev, current) => Math.max(prev, current));
console.log(max); // 9

2. Flattening an array of arrays:

const nested = [[1, 2], [3, 4], [5, 6]];
const flattened = nested.reduce((prev, current) => prev.concat(current));
console.log(flattened); // [1, 2, 3, 4, 5, 6]

3. Counting occurrences of values in an array:

const words = ['apple', 'banana', 'apple', 'cherry', 'banana', 'apple'];
const counts = words.reduce((prev, current) => {
  prev[current] = (prev[current] || 0) + 1;
  return prev;
}, {});
console.log(counts); // { apple: 3, banana: 2, cherry: 1 }

4. Removing duplicates from an array:

const numbers = [1, 2, 3, 2, 1, 4, 5];
const unique = numbers.reduce((prev, current) => {
  if (!prev.includes(current)) {
    prev.push(current);
  }
  return prev;
}, []);
console.log(unique); // [1, 2, 3, 4, 5]

5. Grouping objects by a property:

const people = [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 30 },
  { name: 'Charlie', age: 25 },
  { name: 'Dave', age: 30 }
];
const groups = people.reduce((prev, current) => {
  const key = current.age;
  if (!prev[key]) {
    prev[key] = [];
  }
  prev[key].push(current.name);
  return prev;
}, {});
console.log(groups);
/*
{
  25: ['Alice', 'Charlie'],
  30: ['Bob', 'Dave']
}
*/

These are just a few more examples of the many ways in which the .reduce() function can be used in JavaScript. It's a very versatile method that can help you solve many different problems.