text: export class ObjectData {
  
      constructor(index, type, totalNum, positionFunction) {
          this.index = index;
          this.type = type;
          this.totalNum = totalNum;
          this.positionFunction = positionFunction;
          this.offset = 0;
      }
  
      getType() {
          return this.type;
      }
  
      getTotalNum() {
          return this.totalNum;
      }
  
      getIndex() {
          return this.index;
      }
  
      getNextIndex() {
          return this.index < (this.totalNum - 1) ? this.index + 1 : 0;
      }
  
      getPrevIndex() {
          return this.index > 0 ? this.index - 1 : (this.totalNum - 1);
      }
  
      setIndex(index) {
          this.index = index;
      }
  
      incIndex() {
          this.index = this.getNextIndex();
          return this.index;
      }
  
      getPositionFunction() {
          return this.positionFunction;
      }
  
      getOffset() {
          return this.offset;
      }
  
      setOffset(offset) {
          this.offset = offset;
      }
  
      addToOffset(offset) {
          this.offset += offset;
      }
  }
  