A set of Fibonacci methods using new features of ES2015 (ES6)

Fibonacci.js

{
    class Fibonacci {
        static *inRange(start, end) {
            for(let num of Fibonacci) {
                if(num >= start && num <= end) {
                    yield num;
                } else if(num > end) {
                    break;
                }
            }
        };

        static *getNNumbers(n = 0, start = 0, end = Number.MAX_SAFE_INTEGER) {
            let count = 0;

            for(let num of Fibonacci.inRange(start, end)) {
                if(count <  n) {
                    yield num;
                }
                
                count++;
            }
        };

        static [Symbol.iterator]() {
            let previous = 0;
            let current = 1;

            let first = true;
            let second = true;

            return {
               next () {
                   if(first) {
                        current = 0;
                        first = false;
                   } else if (second) {
                        current = 1;
                        second = false;
                   } else {
                       [previous, current] = [current, previous + current];
                   }

                   return {
                        done: false,
                        value: current
                    };
               }
            }
        };
    };

    let nums = [...Fibonacci.inRange(0, 100)];
    console.log(nums);

    nums = [...Fibonacci.getNNumbers(21)];
    console.log(nums);
}