countBy.md

countBy (source code)

• Curried: true
• Failsafe status: alternative available

The countBy function counts the number of items in an array that match the provided pattern.

Arguments:

• pattern: The pattern using which objects will be matched.
• entityArray: The array of objects from which the objects with the given pattern will be counted.

Usage:

const array = [
  { name: "Oliver", age: 20 },
  { name: "Sam", age: 40 },
  { name: "George", age: 41 },
  { name: "Smith", age: 20 },
];

countBy({ age: 20 }, array); // returns 2
countBy({ age: gt(__, 40) }, array); // returns 1
countBy({ age: 50 }, array); // returns 0