Simple Pager structure in TypeScript

pager.ts

import { modulo } from "./utils";

export class Pager {

  next:number = 0;
  previous:number = 0;

  constructor(public current:number = 0, public length:number = 0, noModulo:boolean = false) {
    this.setNeighbours(noModulo);
  }

  /**
   * Increase current value
   * @param noModulo boolean that tells if the pager is circular
   */
  goNext(noModulo:boolean = false) {
    if (noModulo) {
      if (!this.isLast()) {
        this.setCurrent(this.current +1,noModulo);
      }
    } else {
      this.setCurrent(this.current +1,noModulo);
    }
  }

  /**
   * Decrease current value
   * @param noModulo boolean that tells if the pager is circular
   */
  goPrevious(noModulo:boolean = false) {
    if (noModulo) {
      if (!this.isFirst()) {
        this.setCurrent(this.current -1,noModulo);
      }
    } else {
      this.setCurrent(this.current -1,noModulo);
    }
  }

  isLast(): boolean {
    return this.length > 0 ? this.current === this.length - 1 : true;
  }

  isFirst(): boolean {
    return this.length > 0 ? this.current === 0 : true;
  }

  /**
   * Set current value
   * @param value 
   * @param noModulo boolean that tells if the pager is circular
   */
  setCurrent(value:number, noModulo:boolean = false) {
    if (noModulo) {
      if (value >= 0 && value < this.length) {
        this.current = value;
        this.setNeighbours(noModulo);
      }
    } else {
      this.current = modulo(value,this.length);
      this.setNeighbours(noModulo);
    }
  }

  /**
   * Sets previous and next properties in compliance with current value
   * @param noModulo boolean that tells if the pager is circular
   */
  setNeighbours(noModulo:boolean = false) {
    if (this.length <= 0) return;
    if (noModulo) {
      this.previous = this.current <= 0 ? 0 : this.current-1;
      this.next = this.current >= this.length-1 ? this.length-1 : this.current +1;
    } else {
      this.previous = modulo(this.current -1, this.length);
      this.next = modulo(this.current +1, this.length);
    }
  }

  setLength(value:number, noModulo:boolean = false) {
    if (value >= 0) this.length = value;
    this.setNeighbours(noModulo);
  }
}

utils.ts

/**
 * Returns a value always between 0 and size - 1.
 * @param a current index
 * @param b size
 */
export function modulo(a, b) { return (+a % (b = +b) + b) % b; };