functional Typescript Examples #1

functionalTypescript1.ts

let courses = [
    { name: 'functional fundamentals', enrolled: 2, grade: 100, students: 30 },
    { name: 'category theory', enrolled: 2, grade: 80, students: 25 },
    { name: 'basket weaving', enrolled: 1, grade: 89, students: 43 }
];

function avg(nums: number[]): number {
  const total = nums.reduce((a,b) => a + b, 0);
  return (nums.length == 0) ? 0 : total / nums.length;
}

function pluck<T, K extends keyof T>(objs: T[], key: K): T[K][] {
  return objs.map(obj => obj[key]);
}

let overOneEnrolled = courses.filter(course => course.enrolled > 1);
let averageItem = avg(pluck(overOneEnrolled, 'grade'));