gistfile1.txt

Module
// Core
import { NgModule, Optional, SkipSelf } from '@angular/core';

// Big.js
import Big from 'big.js/big.mjs';

import { BigjsService } from './bigjs.service';

@NgModule({
  providers: [{ provide: 'BigJs', useValue: Big }, BigjsService]
})
export class CoreModule {
  constructor(@Optional() @SkipSelf() parentModule: CoreModule) {
    if (parentModule) {
      throw new Error('CoreModule is already loaded. Import only in AppModule');
    }
  }
}

//Service
import { Inject, Injectable } from '@angular/core';

import Big from 'big.js/big.mjs';
type OgBig = typeof Big;

@Injectable()
export class BigjsService {
  readonly TO_FIXED = 2;
  constructor(@Inject('BigJs') private bj: OgBig) {}

  toStr(value: number | string | OgBig): string {
    if (value instanceof Big) {
      return value.toFixed(this.TO_FIXED);
    }
    return this.bj(value).toFixed(this.TO_FIXED);
  }

  op(num: number | string): OgBig {
    return this.bj(num);
  }

  withSpread(value: string, spread: string): string {
    const valueTimesPlus = this.op(value).times(this.op(100).plus(spread));
    return valueTimesPlus
      .div(100)
      .toFixed(this.TO_FIXED)
      .toString();
  }

  trunc(value: string, digits: number = 0): number {
    const multi = Math.pow(10, digits);
    const v = parseInt(value, 10);
    return Math.trunc(v * multi) / multi;
  }
}