Bill change should be working

Reduce quantity should be working.

bookie/src/app/shared/math.service.spec.ts

@@ -0,0 +1,16 @@
+import { TestBed } from '@angular/core/testing';
+
+import { MathService } from './math.service';
+
+describe('MathService', () => {
+  let service: MathService;
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({});
+    service = TestBed.inject(MathService);
+  });
+
+  it('should be created', () => {
+    expect(service).toBeTruthy();
+  });
+});

bookie/src/app/shared/math.service.ts

@@ -0,0 +1,26 @@
+import { Injectable } from '@angular/core';
+import { evaluate, round } from 'mathjs';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class MathService {
+  // eslint-disable-next-line class-methods-use-this
+  journalAmount(amount: string = '', debit: number): any {
+    const val = this.parseAmount(amount, 2);
+    let newDebit = debit;
+    if (val < 0) {
+      newDebit *= -1;
+    }
+    return { debit: newDebit, amount: Math.abs(val) };
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  parseAmount(amount: string = '', rounding: number = 2): number {
+    const cleaned = `${amount}`.replace(new RegExp('(₹[s]*)|(,)|(s)', 'g'), '');
+    if (cleaned === '') {
+      return 0;
+    }
+    return round(evaluate(cleaned), rounding);
+  }
+}