Code that does not violate SRP

shapes2.js

class AreaCalculator {
  constructor (shapes) {
    this.shapes = shapes
  }

  sum () {
    // logic to calculate the sum of the areas of the provided shapes
  }
}

class CalculatorOutput {
  constructor(areaCalculator) {
    this.areaCalculator = areaCalculator
  }

  toString () {
    return new String(this.areaCalculator.sum())
  }

  toJSON () {
    return {
      sum: this.areaCalculator.sum()
    }
  }
}