gistfile1.js

class Multiplier {
  constructor(value) {
    const coefficient = value
    
    return {
      by(other) {
        return other * coefficient
      },
    }
  }
  
  // by(other) {
    // There's no way to refer the coefficient if you don't want it to be
    // exposed to public. Uncommenting here doen't matter because constructor
    // in JS respects returned variable from it.
  // }
}