Range.js

/**
 * @name range
 * @description 
 * @async
 * @generator
 * @function
 * @param {Object} [context=this] - 
 * @param {number} context.start - The value to use to begin the sequence.
 * @param {number} context.stop - The value to use to stop the sequence.
 * @param {number} context.step - The value to increment n by on each yield
 * @yields {number} n - The next number in the sequence.
 * @return {Promise<T>} this
 */


export default function range(context = this) { return new Range(context)}

class Range {
  constructor(context = this) {
    const {start=0, stop=Infinity, step=1} = context;
    Object.assign(this, {start, stop, step, next: this.next.bind(this)});
  }
  [Symbol.isConcatSpreadable]() {
    return ({
      'number': stop.isFinite(),
      'bigint': true,
    }[stop])
  }
  get[Symbol.toStringTag]() {return 'Range'}
  async * [Symbol.asyncIterator]() {yield* this.next()}
  * [Symbol.iterator]() {yield* this.next()}
  * next() {
    for (let n = this.start; (Math.sign(this.stop - n) == Math.sign(this.step)); n += this.step) {
      yield n;
    }
  }
}