Create new Calculator

Create a constructor function Calculator that creates objects with 3 methods:

read() prompts for two values and saves them as object properties with names a and b respectively.
sum() returns the sum of these properties.
mul() returns the multiplication product of these properties.

For instance:

let calculator = new Calculator();
calculator.read();

alert( "Sum=" + calculator.sum() );
alert( "Mul=" + calculator.mul() );

[demo]