lossless-json/lib/esm/LosslessNumber.test.js

Parse JSON without risk of losing numeric information

import { expect, test } from 'vitest';
import { LosslessNumber, compareLosslessNumber, isLosslessNumber, toLosslessNumber } from './index';
test('create a LosslessNumber from string', () => {
  const n = new LosslessNumber('42');
  expect(n.isLosslessNumber).toBe(true);
  expect(n.value).toBe('42');
});
test('throw an error when when creating a LosslessNumber from invalid string', () => {
  // invalid
  expect(() => new LosslessNumber('a')).toThrow(/Invalid number/);
  expect(() => new LosslessNumber('22.')).toThrow(/Invalid number/);
  expect(() => new LosslessNumber('0.2e')).toThrow(/Invalid number/);
  expect(() => new LosslessNumber('2e3.4')).toThrow(/Invalid number/);
  expect(() => new LosslessNumber('2.3.4')).toThrow(/Invalid number/);
  expect(() => new LosslessNumber('+24')).toThrow(/Invalid number/);
  expect(() => new LosslessNumber('   123')).toThrow(/Invalid number/);
  expect(() => new LosslessNumber('123   ')).toThrow(/Invalid number/);

  // valid
  expect(new LosslessNumber('42e+4').toString()).toEqual('42e+4');
  expect(new LosslessNumber('42E-4').toString()).toEqual('42E-4');
  expect(new LosslessNumber('-42E-4').toString()).toEqual('-42E-4');
});
test('test whether something is a LosslessNumber', () => {
  const n = new LosslessNumber('42');
  expect(isLosslessNumber(n)).toBe(true);
  expect(isLosslessNumber(42)).toBe(false);
  expect(isLosslessNumber(null)).toBe(false);
  expect(isLosslessNumber({})).toBe(false);
  expect(isLosslessNumber([])).toBe(false);
  expect(isLosslessNumber(undefined)).toBe(false);
});
test('create a LosslessNumber from number', () => {
  expect(toLosslessNumber(42)).toEqual(new LosslessNumber('42'));
  expect(toLosslessNumber(2.47)).toEqual(new LosslessNumber('2.47'));
  expect(() => toLosslessNumber(2 / 3)).toThrow('Invalid number: contains more than 15 digits');
  expect(() => toLosslessNumber(Number.NaN)).toThrow('Invalid number: NaN');
  expect(() => toLosslessNumber(Number.POSITIVE_INFINITY)).toThrow('Invalid number: Infinity');
  expect(() => toLosslessNumber(Number.NEGATIVE_INFINITY)).toThrow('Invalid number: -Infinity');
});
test('compareLosslessNumber', () => {
  expect(compareLosslessNumber(new LosslessNumber('5e3'), new LosslessNumber('70'))).toEqual(1);
});
test('use LosslessNumber.valueOf()', () => {
  // safe number
  expect(new LosslessNumber('23.4').valueOf()).toBe(23.4);
  expect(new LosslessNumber('23e4').valueOf()).toBe(230000);

  // a decimal losing insignificant digits
  expect(new LosslessNumber('0.66666666666666666666667').valueOf()).toEqual(0.6666666666666666);

  // a big integer
  expect(new LosslessNumber('123456789012345678901234').valueOf()).toEqual(123456789012345678901234n);

  // overflow
  expect(() => new LosslessNumber('2.3e+500').valueOf()).toThrow("Cannot safely convert to number: the value '2.3e+500' would overflow and become Infinity");

  // underflow
  expect(() => new LosslessNumber('2.3e-500').valueOf()).toThrow("Cannot safely convert to number: the value '2.3e-500' would underflow and become 0");
});
test('can do operations like add a number and a LosslessNumber', () => {
  // @ts-ignore
  expect(new LosslessNumber('3') + 2).toBe(5);
});
test('LosslessNumber - toString', () => {
  expect(new LosslessNumber('23.4').toString()).toBe('23.4');
});
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