Method eachNext

benchmark/data.js:46–52

(fn)

		return this.start < index && index < this.end;
	}
	eachNext(fn) {
		let chunk = this;
		while (chunk) {
			fn(chunk);
			chunk = chunk.next;
		}
	}
	eachPrevious(fn) {
		let chunk = this;
		while (chunk) {