three.js/src/objects/LineLoop.d.ts

import { Line } from './Line';
import { Geometry } from './../core/Geometry';
import { Material } from './../materials/Material';
import { BufferGeometry } from '../core/BufferGeometry';

export class LineLoop extends Line {
  constructor(
    geometry?: Geometry | BufferGeometry,
    material?: Material | Material[]
  );

  type: 'LineLoop';
  isLineLoop: true;
}