An attempt at a super simple money type that only supports addition

simple-money.ts

function toCents(value: number) {
  return Math.round(value * 100);
}

function fromCents(value: number) {
  return +(value / 100).toFixed(2);
}

class Money {
  private cents: number;

  get value() {
    return fromCents(this.cents);
  }

  constructor(value: number) {
    this.cents = toCents(value);
  }

  add(value: number | Money) {
    const addedCents = typeof value === 'number' ? toCents(value) : value.cents;
    const cents = this.cents + addedCents;
    return new Money(fromCents(cents));
  }
}

console.log(0.1 + 0.2);
console.log(new Money(0.1).add(0.2));

// Can try it out here: http://www.typescriptlang.org/play/#code/GYVwdgxgLglg9mABFOBhApmKBnAFANwEMAbEdALkTBAFsAjdAJwEpEBvAKEW8UfShCMkAWUJQAFgDpGccABMCJMogBUiAIwAGTcwDcHAL4cOoSLASJgMmhix4ipClVoMW7Ljz4ChiANSLHRAB6DW1mSRQAMRgAD3QFACY9Q2MIYkJsbERhBHQAT3ceRAAHRhgiKHRECEwcSmp6Jn0PbgBzfkQHMlxWTiKir0EkKzgbWrwJGGxJGrtkoqMW6oRsKEYQaDhGALJ6lyZepaLJ6dmcRABeZDRxnfR5nkWiwjkFLqcG10QAH2zcvMO-R4EBWUEQLzk8Vs5yuUDyxXQcGAnSUVQu6MQAHJPkxMYgAPzXaH2VGsSjvGbjfRA7ggsCrarjS7IcRTSl2Pzg15QqlHTz8IZUdAAdz+YHyuBGYzsuDO2GYD24RkWdOwcGI6EkxDgrVwmkk6k5+qS+lV6s12t14tFOXFeT1BvCEIdSWSQA