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Create an extendable calculator

importance: 5

Create a constructor function Calculator that creates “extendable” calculator objects.

The task consists of two parts.

  1. First, implement the method calculate(str) that takes a string like "1 + 2" in the format “NUMBER operator NUMBER” (space-delimited) and returns the result. Should understand plus + and minus -.

    Usage example:

    let calc = new Calculator;
    alert( calc.calculate("3 + 7") ); // 10
  2. Then add the method addMethod(name, func) that teaches the calculator a new operation. It takes the operator name and the two-argument function func(a,b) that implements it.

    For instance, let’s add the multiplication *, division / and power **:

    let powerCalc = new Calculator;
    powerCalc.addMethod("*", (a, b) => a * b);
    powerCalc.addMethod("/", (a, b) => a / b);
    powerCalc.addMethod("**", (a, b) => a ** b);
    let result = powerCalc.calculate("2 ** 3");
    alert( result ); // 8
  • No brackets or complex expressions in this task.
  • The numbers and the operator are delimited with exactly one space.
  • There may be error handling if you’d like to add it.

Open a sandbox with tests.

  • Please note how methods are stored. They are simply added to the internal object.
  • All tests and numeric conversions are done in the calculate method. In future it may be extended to support more complex expressions.

Open the solution with tests in a sandbox.